PIC16F8X PIC16F83 PIC16F84 PIC16CR83 PIC16CR84 PIC16LF8X PIC16LCR8X PIC16CR8X - Datasheet Archive

 

18-pin Flash/EEPROM 8-Bit Microcontrollers Devices Included in this Data Sheet: Pin Diagrams PIC16F83 PIC16F84 PIC16CR83

 

PIC16F8X PIC16F8X 18-pin Flash/EEPROM 8-Bit Microcontrollers Devices Included in this Data Sheet: Pin Diagrams PIC16F83 PIC16F83 PIC16F84 PIC16F84 PIC16CR83 PIC16CR83 PIC16CR84 PIC16CR84 Extended voltage range devices available (PIC16LF8X PIC16LF8X, PIC16LCR8X PIC16LCR8X) PDIP, SOIC RA2 Device Program Memory (words) Data Data RAM EEPROM (bytes) (bytes) 36 64 68 64 10 PIC16CR83 PIC16CR83 512 ROM 36 64 10 PIC16CR84 PIC16CR84 1 K ROM 68 64 10 · · · · · · 10 14-bit wide instructions 8-bit wide data path 15 special function hardware registers Eight-level deep hardware stack Direct, indirect and relative addressing modes Four interrupt sources: - External RB0/INT pin - TMR0 timer overflow - PORTB interrupt on change - Data EEPROM write complete · 1000 erase/write cycles Flash program memory · 10,000,000 erase/write cycles EEPROM data memory · EEPROM Data Retention > 40 years Peripheral Features: OSC2/CLKOUT 5 14 VDD 6 13 RB7 7 12 RB6 8 11 RB5 RB3 512 Flash 15 RB2 1 K Flash OSC1/CLKIN 4 RB1 PIC16F84 PIC16F84 16 RB0/INT PIC16F83 PIC16F83 RA0 3 VSS Max. Freq (MHz) RA1 17 MCLR · Only 35 single word instructions to learn · All instructions single cycle except for program branches which are two-cycle · Operating speed: DC - 10 MHz clock input DC - 400 ns instruction cycle 18 2 RA4/T0CKI High Performance RISC CPU Features: ·1 RA3 9 10 RB4 PIC16F8X PIC16F8X PIC16CR8X PIC16CR8X · · · · · Special Microcontroller Features: · In-Circuit Serial Programming (ICSPTM) - via two pins (ROM devices support only Data EEPROM programming) · Power-on Reset (POR) · Power-up Timer (PWRT) · Oscillator Start-up Timer (OST) · Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation · Code-protection · Power saving SLEEP mode · Selectable oscillator options CMOS Flash/EEPROM Technology: · Low-power, high-speed technology · Fully static design · Wide operating voltage range: - Commercial: 2.0V to 6.0V - Industrial: 2.0V to 6.0V · Low power consumption: - < 2 mA typical @ 5V, 4 MHz - 15 µA typical @ 2V, 32 kHz - < 1 µA typical standby current @ 2V · 13 I/O pins with individual direction control · High current sink/source for direct LED drive - 25 mA sink max. per pin - 20 mA source max. per pin · TMR0: 8-bit timer/counter with 8-bit programmable prescaler © 1998 Microchip Technology Inc. DS30430C-page 1 PIC16F8X PIC16F8X Table of Contents 1.0 General Description . 3 2.0 PIC16F8X PIC16F8X Device Varieties . 5 3.0 Architectural Overview. 7 4.0 Memory Organization . 11 5.0 I/O Ports. 21 6.0 Timer0 Module and TMR0 Register. 27 7.0 Data EEPROM Memory. 33 8.0 Special Features of the CPU . 37 9.0 Instruction Set Summary . 53 10.0 Development Support . 69 11.0 Electrical Characteristics for PIC16F83 PIC16F83 and PIC16F84 PIC16F84. 73 12.0 Electrical Characteristics for PIC16CR83 PIC16CR83 and PIC16CR84 PIC16CR84. 85 13.0 DC & AC Characteristics Graphs/Tables. 97 14.0 Packaging Information . 109 Appendix A: Feature Improvements - From PIC16C5X PIC16C5X To PIC16F8X PIC16F8X . 113 Appendix B: Code Compatibility - from PIC16C5X PIC16C5X to PIC16F8X PIC16F8X. 113 Appendix C: What's New In This Data Sheet . 114 Appendix D: What's Changed In This Data Sheet . 114 Appendix E: Conversion Considerations - PIC16C84 PIC16C84 to PIC16F83/F84 PIC16F83/F84 And PIC16CR83/CR84 PIC16CR83/CR84. 115 Index . 117 On-Line Support. 119 Reader Response . 120 PIC16F8X PIC16F8X Product Identification System . 121 Sales and Support. 121 To Our Valued Customers We constantly strive to improve the quality of all our products and documentation. We have spent a great deal of time to ensure that these documents are correct. However, we realize that we may have missed a few things. If you find any information that is missing or appears in error, please use the reader response form in the back of this data sheet to inform us. We appreciate your assistance in making this a better document. DS30430C-page 2 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 1.0 GENERAL DESCRIPTION The PIC16F8X PIC16F8X is a group in the PIC16CXX PIC16CXX family of low-cost, high-performance, CMOS, fully-static, 8-bit microcontrollers. This group contains the following devices: · · · · PIC16F83 PIC16F83 PIC16F84 PIC16F84 PIC16CR83 PIC16CR83 PIC16CR84 PIC16CR84 All PICmicroTM microcontrollers employ an advanced RISC architecture. PIC16F8X PIC16F8X devices have enhanced core features, eight-level deep stack, and multiple internal and external interrupt sources. The separate instruction and data buses of the Harvard architecture allow a 14-bit wide instruction word with a separate 8-bit wide data bus. The two stage instruction pipeline allows all instructions to execute in a single cycle, except for program branches (which require two cycles). A total of 35 instructions (reduced instruction set) are available. Additionally, a large register set is used to achieve a very high performance level. PIC16F8X PIC16F8X microcontrollers typically achieve a 2:1 code compression and up to a 4:1 speed improvement (at 20 MHz) over other 8-bit microcontrollers in their class. The PIC16F8X PIC16F8X has up to 68 bytes of RAM, 64 bytes of Data EEPROM memory, and 13 I/O pins. A timer/ counter is also available. The PIC16CXX PIC16CXX family has special features to reduce external components, thus reducing cost, enhancing system reliability and reducing power consumption. There are four oscillator options, of which the single pin RC oscillator provides a low-cost solution, the LP oscillator minimizes power consumption, XT is a standard crystal, and the HS is for High Speed crystals. The SLEEP (power-down) mode offers power saving. The user can wake the chip from sleep through several external and internal interrupts and resets. A highly reliable Watchdog Timer with its own on-chip RC oscillator provides protection against software lockup. Table 1-1 lists the features of the PIC16F8X PIC16F8X. A simplified block diagram of the PIC16F8X PIC16F8X is shown in Figure 3-1. The PIC16F8X PIC16F8X fits perfectly in applications ranging from high speed automotive and appliance motor control to low-power remote sensors, electronic locks, security devices and smart cards. The Flash/EEPROM technology makes customization of application programs (transmitter codes, motor speeds, receiver frequencies, security codes, etc.) extremely fast and convenient. The small footprint packages make this microcontroller series perfect for all applications with space limitations. Low-cost, low-power, high performance, ease-of-use and I/O flexibility make the PIC16F8X PIC16F8X very versatile even in areas where no microcontroller use has been considered before (e.g., timer functions; serial communication; capture, compare and PWM functions; and co-processor applications). The serial in-system programming feature (via two pins) offers flexibility of customizing the product after complete assembly and testing. This feature can be used to serialize a product, store calibration data, or program the device with the current firmware before shipping. 1.1 Family and Upward Compatibility Those users familiar with the PIC16C5X PIC16C5X family of microcontrollers will realize that this is an enhanced version of the PIC16C5X PIC16C5X architecture. Please refer to Appendix A for a detailed list of enhancements. Code written for PIC16C5X PIC16C5X devices can be easily ported to PIC16F8X PIC16F8X devices (Appendix B). 1.2 Development Support The PIC16CXX PIC16CXX family is supported by a full-featured macro assembler, a software simulator, an in-circuit emulator, a low-cost development programmer and a full-featured programmer. A "C" compiler and fuzzy logic support tools are also available. The devices with Flash program memory allow the same device package to be used for prototyping and production. In-circuit reprogrammability allows the code to be updated without the device being removed from the end application. This is useful in the development of many applications where the device may not be easily accessible, but the prototypes may require code updates. This is also useful for remote applications where the code may need to be updated (such as rate information). © 1998 Microchip Technology Inc. DS30430C-page 3 PIC16F8X PIC16F8X TABLE 1-1 PIC16F8X PIC16F8X FAMILY OF DEVICES PIC16F83 PIC16F83 Clock Maximum Frequency of Operation (MHz) 10 PIC16CR83 PIC16CR83 10 PIC16F84 PIC16F84 10 PIC16CR84 PIC16CR84 10 Flash Program Memory Memory 512 - 1K - EEPROM Program Memory - - - - ROM Program Memory - 512 - 1K Data Memory (bytes) 36 36 68 68 Data EEPROM (bytes) 64 64 64 64 TMR0 TMR0 TMR0 TMR0 Interrupt Sources 4 4 4 4 I/O Pins 13 13 13 13 Voltage Range (Volts) 2.0-6.0 2.0-6.0 2.0-6.0 2.0-6.0 Packages 18-pin DIP, SOIC 18-pin DIP, SOIC 18-pin DIP, SOIC 18-pin DIP, SOIC Peripherals Timer Module(s) Features All PICmicroTM Family devices have Power-on Reset, selectable Watchdog Timer, selectable code protect and high I/O current capability. All PIC16F8X PIC16F8X Family devices use serial programming with clock pin RB6 and data pin RB7. DS30430C-page 4 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 2.0 PIC16F8X PIC16F8X DEVICE VARIETIES A variety of frequency ranges and packaging options are available. Depending on application and production requirements the proper device option can be selected using the information in this section. When placing orders, please use the "PIC16F8X PIC16F8X Product Identification System" at the back of this data sheet to specify the correct part number. There are four device "types" as indicated in the device number. 1. 2. 3. 4. F, as in PIC16F84 PIC16F84. These devices have Flash program memory and operate over the standard voltage range. LF, as in PIC16LF84 PIC16LF84. These devices have Flash program memory and operate over an extended voltage range. CR, as in PIC16CR83 PIC16CR83. These devices have ROM program memory and operate over the standard voltage range. LCR, as in PIC16LCR84 PIC16LCR84. These devices have ROM program memory and operate over an extended voltage range. When discussing memory maps and other architectural features, the use of F and CR also implies the LF and LCR versions. 2.1 2.3 Serialized Quick-TurnaroundProduction (SQTP SM ) Devices Microchip offers the unique programming service where a few user-defined locations in each device are programmed with different serial numbers. The serial numbers may be random, pseudo-random or sequential. Serial programming allows each device to have a unique number which can serve as an entry-code, password or ID number. For information on submitting a SQTP code, please contact your Microchip Regional Sales Office. 2.4 ROM Devices Some of Microchip's devices have a corresponding device where the program memory is a ROM. These devices give a cost savings over Microchip's traditional user programmed devices (EPROM, EEPROM). ROM devices (PIC16CR8X PIC16CR8X) do not allow serialization information in the program memory space. The user may program this information into the Data EEPROM. For information on submitting a ROM code, please contact your Microchip Regional Sales Office. Flash Devices These devices are offered in the lower cost plastic package, even though the device can be erased and reprogrammed. This allows the same device to be used for prototype development and pilot programs as well as production. A further advantage of the electrically-erasable Flash version is that it can be erased and reprogrammed incircuit, or by device programmers, such as Microchip's PICSTART® Plus or PRO MATE® II programmers. 2.2 Quick-Turnaround-Production (QTP) Devices Microchip offers a QTP Programming Service for factory production orders. This service is made available for users who choose not to program a medium to high quantity of units and whose code patterns have stabilized. The devices have all Flash locations and configuration options already programmed by the factory. Certain code and prototype verification procedures do apply before production shipments are available. For information on submitting a QTP code, please contact your Microchip Regional Sales Office. © 1998 Microchip Technology Inc. DS30430C-page 5 PIC16F8X PIC16F8X NOTES: DS30430C-page 6 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 3.0 ARCHITECTURAL OVERVIEW The high performance of the PIC16CXX PIC16CXX family can be attributed to a number of architectural features commonly found in RISC microprocessors. To begin with, the PIC16CXX PIC16CXX uses a Harvard architecture. This architecture has the program and data accessed from separate memories. So the device has a program memory bus and a data memory bus. This improves bandwidth over traditional von Neumann architecture where program and data are fetched from the same memory (accesses over the same bus). Separating program and data memory further allows instructions to be sized differently than the 8-bit wide data word. PIC16CXX PIC16CXX opcodes are 14-bits wide, enabling single word instructions. The full 14-bit wide program memory bus fetches a 14-bit instruction in a single cycle. A twostage pipeline overlaps fetch and execution of instructions (Example 3-1). Consequently, all instructions execute in a single cycle except for program branches. The PIC16F83 PIC16F83 and PIC16CR83 PIC16CR83 address 512 x 14 of program memory, and the PIC16F84 PIC16F84 and PIC16CR84 PIC16CR84 address 1K x 14 program memory. All program memory is internal. The PIC16CXX PIC16CXX can directly or indirectly address its register files or data memory. All special function registers including the program counter are mapped in the data memory. An orthogonal (symmetrical) instruction set makes it possible to carry out any operation on any register using any addressing mode. This symmetrical nature and lack of `special optimal situations' make programming with the PIC16CXX PIC16CXX simple yet efficient. In addition, the learning curve is reduced significantly. © 1998 Microchip Technology Inc. DS30430C-page 7 PIC16F8X PIC16F8X PIC16CXX PIC16CXX devices contain an 8-bit ALU and working register. The ALU is a general purpose arithmetic unit. It performs arithmetic and Boolean functions between data in the working register and any register file. The W register is an 8-bit working register used for ALU operations. It is not an addressable register. Depending on the instruction executed, the ALU may affect the values of the Carry (C), Digit Carry (DC), and Zero (Z) bits in the STATUS register. The C and DC bits operate as a borrow and digit borrow out bit, respectively, in subtraction. See the SUBLW and SUBWF instructions for examples. The ALU is 8-bits wide and capable of addition, subtraction, shift and logical operations. Unless otherwise mentioned, arithmetic operations are two's complement in nature. In two-operand instructions, typically one operand is the working register (W register), and the other operand is a file register or an immediate constant. In single operand instructions, the operand is either the W register or a file register. FIGURE 3-1: PIC16F8X PIC16F8X BLOCK DIAGRAM Data Bus 13 8 Program Counter Flash/ROM Program Memory PIC16F83/CR83 PIC16F83/CR83 512 x 14 PIC16F84/CR84 PIC16F84/CR84 1K x 14 Program Bus A simplified block diagram for the PIC16F8X PIC16F8X is shown in Figure 3-1, its corresponding pin description is shown in Table 3-1. 8 Level Stack (13-bit) 14 EEPROM Data Memory RAM File Registers PIC16F83/CR83 PIC16F83/CR83 36 x 8 PIC16F84/CR84 PIC16F84/CR84 68 x 8 7 EEDATA RAM Addr EEPROM Data Memory 64 x 8 EEADR Addr Mux Instruction reg 7 Direct Addr 5 TMR0 Indirect Addr FSR reg RA4/T0CKI STATUS reg 8 MUX Power-up Timer Instruction Decode & Control Timing Generation Oscillator Start-up Timer 8 ALU Power-on Reset Watchdog Timer I/O Ports RA3:RA0 W reg RB7:RB1 RB0/INT OSC2/CLKOUT OSC1/CLKIN DS30430C-page 8 MCLR VDD, VSS © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X TABLE 3-1 PIC16F8X PIC16F8X PINOUT DESCRIPTION DIP No. SOIC No. I/O/P Type OSC1/CLKIN 16 16 I OSC2/CLKOUT 15 15 O - Oscillator crystal output. Connects to crystal or resonator in crystal oscillator mode. In RC mode, OSC2 pin outputs CLKOUT which has 1/4 the frequency of OSC1, and denotes the instruction cycle rate. MCLR 4 4 I/P ST Master clear (reset) input/programming voltage input. This pin is an active low reset to the device. Pin Name Buffer Type Description ST/CMOS (3) Oscillator crystal input/external clock source input. PORTA is a bi-directional I/O port. RA0 17 17 I/O TTL RA1 18 18 I/O TTL RA2 1 1 I/O TTL RA3 2 2 I/O TTL RA4/T0CKI 3 3 I/O ST Can also be selected to be the clock input to the TMR0 timer/ counter. Output is open drain type. PORTB is a bi-directional I/O port. PORTB can be software programmed for internal weak pull-up on all inputs. RB0/INT 6 6 I/O TTL/ST (1) RB1 7 7 I/O TTL RB2 8 8 I/O TTL RB0/INT can also be selected as an external interrupt pin. RB3 9 9 I/O TTL RB4 10 10 I/O TTL Interrupt on change pin. RB5 11 11 I/O TTL Interrupt on change pin. RB6 12 12 I/O TTL/ST (2) (2) TTL/ST Interrupt on change pin. Serial programming clock. Interrupt on change pin. Serial programming data. RB7 13 13 I/O VSS 5 5 P - Ground reference for logic and I/O pins. VDD 14 14 P - Positive supply for logic and I/O pins. Legend: I= input O = output I/O = Input/Output P = power - = Not used TTL = TTL input ST = Schmitt Trigger input Note 1: This buffer is a Schmitt Trigger input when configured as the external interrupt. 2: This buffer is a Schmitt Trigger input when used in serial programming mode. 3: This buffer is a Schmitt Trigger input when configured in RC oscillator mode and a CMOS input otherwise. © 1998 Microchip Technology Inc. DS30430C-page 9 PIC16F8X PIC16F8X 3.1 Clocking Scheme/Instruction Cycle 3.2 The clock input (from OSC1) is internally divided by four to generate four non-overlapping quadrature clocks namely Q1, Q2, Q3 and Q4. Internally, the program counter (PC) is incremented every Q1, the instruction is fetched from the program memory and latched into the instruction register in Q4. The instruction is decoded and executed during the following Q1 through Q4. The clocks and instruction execution flow is shown in Figure 3-2. Instruction Flow/Pipelining An "Instruction Cycle" consists of four Q cycles (Q1, Q2, Q3 and Q4). The instruction fetch and execute are pipelined such that fetch takes one instruction cycle while decode and execute takes another instruction cycle. However, due to the pipelining, each instruction effectively executes in one cycle. If an instruction causes the program counter to change (e.g., GOTO) then two cycles are required to complete the instruction (Example 3-1). A fetch cycle begins with the Program Counter (PC) incrementing in Q1. In the execution cycle, the fetched instruction is latched into the "Instruction Register" in cycle Q1. This instruction is then decoded and executed during the Q2, Q3, and Q4 cycles. Data memory is read during Q2 (operand read) and written during Q4 (destination write). FIGURE 3-2: CLOCK/INSTRUCTION CYCLE Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 OSC1 Q1 Q2 Internal phase clock Q3 Q4 PC PC OSC2/CLKOUT (RC mode) EXAMPLE 3-1: Fetch INST (PC) Execute INST (PC-1) PC+2 Fetch INST (PC+1) Execute INST (PC) Fetch INST (PC+2) Execute INST (PC+1) INSTRUCTION PIPELINE FLOW 1. MOVLW 55h 2. MOVWF PORTB 3. CALL SUB_1 4. BSF PC+1 PORTA, BIT3 Fetch 1 Execute 1 Fetch 2 Execute 2 Fetch 3 Execute 3 Fetch 4 Flush Fetch SUB_1 Execute SUB_1 All instructions are single cycle, except for any program branches. These take two cycles since the fetch instruction is "flushed" from the pipeline while the new instruction is being fetched and then executed. DS30430C-page 10 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X MEMORY ORGANIZATION There are two memory blocks in the PIC16F8X PIC16F8X. These are the program memory and the data memory. Each block has its own bus, so that access to each block can occur during the same oscillator cycle. The data memory can further be broken down into the general purpose RAM and the Special Function Registers (SFRs). The operation of the SFRs that control the "core" are described here. The SFRs used to control the peripheral modules are described in the section discussing each individual peripheral module. The data memory area also contains the data EEPROM memory. This memory is not directly mapped into the data memory, but is indirectly mapped. That is, an indirect address pointer specifies the address of the data EEPROM memory to read/write. The 64 bytes of data EEPROM memory have the address range 0h-3Fh. More details on the EEPROM memory can be found in Section 7.0. 4.1 FIGURE 4-1: PROGRAM MEMORY MAP AND STACK - PIC16F83/CR83 PIC16F83/CR83 PC 13 CALL, RETURN RETFIE, RETLW Stack Level 1 · · · Stack Level 8 Reset Vector User Memory Space 4.0 0000h Peripheral Interrupt Vector 0004h 1FFh Program Memory Organization The PIC16FXX PIC16FXX has a 13-bit program counter capable of addressing an 8K x 14 program memory space. For the PIC16F83 PIC16F83 and PIC16CR83 PIC16CR83, the first 512 x 14 (0000h-01FFh) are physically implemented (Figure 4-1). For the PIC16F84 PIC16F84 and PIC16CR84 PIC16CR84, the first 1K x 14 (0000h-03FFh) are physically implemented (Figure 4-2). Accessing a location above the physically implemented address will cause a wraparound. For example, for the PIC16F84 PIC16F84 locations 20h, 420h, 820h, C20h, 1020h, 1420h, 1820h, and 1C20h will be the same instruction. 1FFFh FIGURE 4-2: PROGRAM MEMORY MAP AND STACK - PIC16F84/CR84 PIC16F84/CR84 PC 13 CALL, RETURN RETFIE, RETLW Stack Level 1 · · · Stack Level 8 The reset vector is at 0000h and the interrupt vector is at 0004h. 0000h Peripheral Interrupt Vector 0004h User Memory Space Reset Vector 3FFh 1FFFh © 1998 Microchip Technology Inc. DS30430C-page 11 PIC16F8X PIC16F8X 4.2 Data Memory Organization 4.2.1 GENERAL PURPOSE REGISTER FILE The data memory is partitioned into two areas. The first is the Special Function Registers (SFR) area, while the second is the General Purpose Registers (GPR) area. The SFRs control the operation of the device. All devices have some amount of General Purpose Register (GPR) area. Each GPR is 8 bits wide and is accessed either directly or indirectly through the FSR (Section 4.5). Portions of data memory are banked. This is for both the SFR area and the GPR area. The GPR area is banked to allow greater than 116 bytes of general purpose RAM. The banked areas of the SFR are for the registers that control the peripheral functions. Banking requires the use of control bits for bank selection. These control bits are located in the STATUS Register. Figure 4-1 and Figure 4-2 show the data memory map organization. The GPR addresses in bank 1 are mapped to addresses in bank 0. As an example, addressing location 0Ch or 8Ch will access the same GPR. Instructions MOVWF and MOVF can move values from the W register to any location in the register file ("F"), and vice-versa. The special function registers can be classified into two sets, core and peripheral. Those associated with the core functions are described in this section. Those related to the operation of the peripheral features are described in the section for that specific feature. The entire data memory can be accessed either directly using the absolute address of each register file or indirectly through the File Select Register (FSR) (Section 4.5). Indirect addressing uses the present value of the RP1:RP0 bits for access into the banked areas of data memory. 4.2.2 SPECIAL FUNCTION REGISTERS The Special Function Registers (Figure 4-1, Figure 4-2 and Table 4-1) are used by the CPU and Peripheral functions to control the device operation. These registers are static RAM. Data memory is partitioned into two banks which contain the general purpose registers and the special function registers. Bank 0 is selected by clearing the RP0 bit (STATUS). Setting the RP0 bit selects Bank 1. Each Bank extends up to 7Fh (128 bytes). The first twelve locations of each Bank are reserved for the Special Function Registers. The remainder are General Purpose Registers implemented as static RAM. DS30430C-page 12 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X FIGURE 4-1: REGISTER FILE MAP PIC16F83/CR83 PIC16F83/CR83 File Address FIGURE 4-2: REGISTER FILE MAP PIC16F84/CR84 PIC16F84/CR84 File Address File Address 80h 00h Indirect addr.(1) OPTION 81h 01h TMR0 OPTION 81h PCL 82h 02h PCL PCL 82h STATUS STATUS 83h 03h STATUS STATUS 83h FSR FSR 84h 04h FSR FSR 84h 05h PORTA TRISA 85h 05h PORTA TRISA 85h 06h PORTB TRISB 86h 06h PORTB TRISB 86h 87h 07h 08h EEDATA EECON1 88h 08h EEDATA EECON1 88h 09h EEADR EECON2(1) 89h 09h EEADR EECON2(1) 89h 0Ah PCLATH PCLATH 8Ah 0Ah PCLATH PCLATH 8Ah 0Bh INTCON INTCON 8Bh 0Bh INTCON INTCON 8Bh 8Ch 0Ch 00h Indirect addr.(1) 01h TMR0 02h PCL 03h 04h Indirect addr.(1) 07h 0Ch 36 General Purpose registers (SRAM) Mapped (accesses) in Bank 0 2Fh 30h File Address 8Ch Mapped (accesses) in Bank 0 4Fh 50h 7Fh FFh Bank 0 Bank 1 Unimplemented data memory location; read as '0'. Note 1: Not a physical register. © 1998 Microchip Technology Inc. 80h 87h 68 General Purpose registers (SRAM) AFh B0h Indirect addr.(1) CFh D0h 7Fh FFh Bank 0 Bank 1 Unimplemented data memory location; read as '0'. Note 1: Not a physical register. DS30430C-page 13 PIC16F8X PIC16F8X TABLE 4-1 Address REGISTER FILE SUMMARY Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on Power-on Reset Value on all other resets (Note3) Bank 0 00h INDF Uses contents of FSR to address data memory (not a physical register) - - - - 01h TMR0 8-bit real-time clock/counter xxxx xxxx uuuu uuuu 02h PCL Low order 8 bits of the Program Counter (PC) 0000 0000 0000 0000 (2) IRP RP1 TO RP0 PD Z DC 03h STATUS 04h FSR 05h PORTA - - - RA4/T0CKI RA3 RA2 RA1 06h PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 C 000q quuu uuuu uuuu RA0 -x xxxx -u uuuu RB0/INT xxxx xxxx uuuu uuuu Unimplemented location, read as '0' 07h 0001 1xxx xxxx xxxx - - - - Indirect data memory address pointer 0 08h EEDATA EEPROM data register xxxx xxxx uuuu uuuu 09h EEADR EEPROM address register xxxx xxxx uuuu uuuu 0Ah PCLATH - - - -0 0000 -0 0000 0Bh INTCON GIE EEIE T0IE 0000 000x 0000 000u - - - - 1111 1111 1111 1111 0000 0000 0000 0000 Write buffer for upper 5 bits of the PC (1) INTE RBIE T0IF INTF RBIF Bank 1 80h INDF 81h OPTION_ REG 82h PCL 83h STATUS (2) 84h FSR 85h TRISA 86h TRISB RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 Low order 8 bits of Program Counter (PC) IRP RP1 RP0 TO PD Z DC C - - - 000q quuu uuuu uuuu -1 1111 PORTA data direction register 0001 1xxx xxxx xxxx Indirect data memory address pointer 0 -1 1111 EECON1 PORTB data direction register 1111 1111 1111 1111 Unimplemented location, read as '0' 87h 88h Uses contents of FSR to address data memory (not a physical register) - - - - -0 x000 -0 q000 - - - 89h EECON2 0Ah PCLATH - - - 0Bh INTCON GIE EEIE T0IE EEIF WRERR WREN WR RD EEPROM control register 2 (not a physical register) - - INTE RBIE T0IF INTF RBIF - - -0 0000 Write buffer for upper 5 bits of the PC (1) -0 0000 0000 000x 0000 000u Legend: x = unknown, u = unchanged. - = unimplemented read as '0', q = value depends on condition. Note 1: The upper byte of the program counter is not directly accessible. PCLATH is a slave register for PC. The contents of PCLATH can be transferred to the upper byte of the program counter, but the contents of PC is never transferred to PCLATH. 2: The TO and PD status bits in the STATUS register are not affected by a MCLR reset. 3: Other (non power-up) resets include: external reset through MCLR and the Watchdog Timer Reset. DS30430C-page 14 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 4.2.2.1 STATUS REGISTER The STATUS register contains the arithmetic status of the ALU, the RESET status and the bank select bit for data memory. As with any register, the STATUS register can be the destination for any instruction. If the STATUS register is the destination for an instruction that affects the Z, DC or C bits, then the write to these three bits is disabled. These bits are set or cleared according to device logic. Furthermore, the TO and PD bits are not writable. Therefore, the result of an instruction with the STATUS register as destination may be different than intended. For example, CLRF STATUS will clear the upper-three bits and set the Z bit. This leaves the STATUS register as 000u u1uu (where u = unchanged). FIGURE 4-1: R/W-0 IRP Only the BCF, BSF, SWAPF and MOVWF instructions should be used to alter the STATUS register (Table 9-2) because these instructions do not affect any status bit. Note 1: The IRP and RP1 bits (STATUS) are not used by the PIC16F8X PIC16F8X and should be programmed as cleared. Use of these bits as general purpose R/W bits is NOT recommended, since this may affect upward compatibility with future products. Note 2: The C and DC bits operate as a borrow and digit borrow out bit, respectively, in subtraction. See the SUBLW and SUBWF instructions for examples. Note 3: When the STATUS register is the destination for an instruction that affects the Z, DC or C bits, then the write to these three bits is disabled. The specified bit(s) will be updated according to device logic STATUS REGISTER (ADDRESS 03h, 83h) R/W-0 RP1 R/W-0 RP0 R-1 TO R-1 PD R/W-x Z R/W-x DC bit7 bit 7: R/W-x C bit0 R = Readable bit W = Writable bit U = Unimplemented bit, read as `0' - n = Value at POR reset IRP: Register Bank Select bit (used for indirect addressing) 0 = Bank 0, 1 (00h - FFh) 1 = Bank 2, 3 (100h - 1FFh) The IRP bit is not used by the PIC16F8X PIC16F8X. IRP should be maintained clear. bit 6-5: RP1:RP0: Register Bank Select bits (used for direct addressing) 00 = Bank 0 (00h - 7Fh) 01 = Bank 1 (80h - FFh) 10 = Bank 2 (100h - 17Fh) 11 = Bank 3 (180h - 1FFh) Each bank is 128 bytes. Only bit RP0 is used by the PIC16F8X PIC16F8X. RP1 should be maintained clear. bit 4: TO: Time-out bit 1 = After power-up, CLRWDT instruction, or SLEEP instruction 0 = A WDT time-out occurred bit 3: PD: Power-down bit 1 = After power-up or by the CLRWDT instruction 0 = By execution of the SLEEP instruction bit 2: Z: Zero bit 1 = The result of an arithmetic or logic operation is zero 0 = The result of an arithmetic or logic operation is not zero bit 1: DC: Digit carry/borrow bit (for ADDWF and ADDLW instructions) (For borrow the polarity is reversed) 1 = A carry-out from the 4th low order bit of the result occurred 0 = No carry-out from the 4th low order bit of the result bit 0: C: Carry/borrow bit (for ADDWF and ADDLW instructions) 1 = A carry-out from the most significant bit of the result occurred 0 = No carry-out from the most significant bit of the result occurred Note:For borrow the polarity is reversed. A subtraction is executed by adding the two's complement of the second operand. For rotate (RRF, RLF) instructions, this bit is loaded with either the high or low order bit of the source register. © 1998 Microchip Technology Inc. DS30430C-page 15 PIC16F8X PIC16F8X 4.2.2.2 OPTION_REG REGISTER Note: The OPTION_REG register is a readable and writable register which contains various control bits to configure the TMR0/WDT prescaler, the external INT interrupt, TMR0, and the weak pull-ups on PORTB. FIGURE 4-1: When the prescaler is assigned to the WDT (PSA = '1'), TMR0 has a 1:1 prescaler assignment. OPTION_REG REGISTER (ADDRESS 81h) R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 bit7 bit0 bit 7: RBPU: PORTB Pull-up Enable bit 1 = PORTB pull-ups are disabled 0 = PORTB pull-ups are enabled (by individual port latch values) bit 6: INTEDG: Interrupt Edge Select bit 1 = Interrupt on rising edge of RB0/INT pin 0 = Interrupt on falling edge of RB0/INT pin bit 5: T0CS: TMR0 Clock Source Select bit 1 = Transition on RA4/T0CKI pin 0 = Internal instruction cycle clock (CLKOUT) bit 4: T0SE: TMR0 Source Edge Select bit 1 = Increment on high-to-low transition on RA4/T0CKI pin 0 = Increment on low-to-high transition on RA4/T0CKI pin bit 3: R = Readable bit W = Writable bit U = Unimplemented bit, read as `0' - n = Value at POR reset PSA: Prescaler Assignment bit 1 = Prescaler assigned to the WDT 0 = Prescaler assigned to TMR0 bit 2-0: PS2:PS0: Prescaler Rate Select bits Bit Value 000 001 010 011 100 101 110 111 DS30430C-page 16 TMR0 Rate 1:2 1:4 1:8 1 : 16 1 : 32 1 : 64 1 : 128 1 : 256 WDT Rate 1:1 1:2 1:4 1:8 1 : 16 1 : 32 1 : 64 1 : 128 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 4.2.2.3 INTCON REGISTER Note: The INTCON register is a readable and writable register which contains the various enable bits for all interrupt sources. FIGURE 4-1: Interrupt flag bits get set when an interrupt condition occurs regardless of the state of its corresponding enable bit or the global enable bit, GIE (INTCON). INTCON REGISTER (ADDRESS 0Bh, 8Bh) R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-x GIE EEIE T0IE INTE RBIE T0IF INTF RBIF bit7 bit 7: bit0 R = Readable bit W = Writable bit U = Unimplemented bit, read as `0' - n = Value at POR reset GIE: Global Interrupt Enable bit 1 = Enables all un-masked interrupts 0 = Disables all interrupts Note: For the operation of the interrupt structure, please refer to Section 8.5. bit 6: EEIE: EE Write Complete Interrupt Enable bit 1 = Enables the EE write complete interrupt 0 = Disables the EE write complete interrupt bit 5: T0IE: TMR0 Overflow Interrupt Enable bit 1 = Enables the TMR0 interrupt 0 = Disables the TMR0 interrupt bit 4: INTE: RB0/INT Interrupt Enable bit 1 = Enables the RB0/INT interrupt 0 = Disables the RB0/INT interrupt bit 3: RBIE: RB Port Change Interrupt Enable bit 1 = Enables the RB port change interrupt 0 = Disables the RB port change interrupt bit 2: T0IF: TMR0 overflow interrupt flag bit 1 = TMR0 has overflowed (must be cleared in software) 0 = TMR0 did not overflow bit 1: INTF: RB0/INT Interrupt Flag bit 1 = The RB0/INT interrupt occurred 0 = The RB0/INT interrupt did not occur bit 0: RBIF: RB Port Change Interrupt Flag bit 1 = When at least one of the RB7:RB4 pins changed state (must be cleared in software) 0 = None of the RB7:RB4 pins have changed state © 1998 Microchip Technology Inc. DS30430C-page 17 PIC16F8X PIC16F8X 4.3 Program Counter: PCL and PCLATH The Program Counter (PC) is 13-bits wide. The low byte is the PCL register, which is a readable and writable register. The high byte of the PC (PC) is not directly readable nor writable and comes from the PCLATH register. The PCLATH (PC latch high) register is a holding register for PC. The contents of PCLATH are transferred to the upper byte of the program counter when the PC is loaded with a new value. This occurs during a CALL, GOTO or a write to PCL. The high bits of PC are loaded from PCLATH as shown in Figure 4-1. FIGURE 4-1: LOADING OF PC IN DIFFERENT SITUATIONS PCH 12 PCL 8 7 0 INST with PCL as dest PC 8 PCLATH 5 ALU result manipulation of the PCLATH is not required for the return instructions (which "pops" the PC from the stack). Note: 4.4 The PIC16F8X PIC16F8X ignores the PCLATH bits, which are used for program memory pages 1, 2 and 3 (0800h - 1FFFh). The use of PCLATH as general purpose R/W bits is not recommended since this may affect upward compatibility with future products. Stack The PIC16FXX PIC16FXX has an 8 deep x 13-bit wide hardware stack (Figure 4-1). The stack space is not part of either program or data space and the stack pointer is not readable or writable. The entire 13-bit PC is "pushed" onto the stack when a CALL instruction is executed or an interrupt is acknowledged. The stack is "popped" in the event of a RETURN, RETLW or a RETFIE instruction execution. PCLATH is not affected by a push or a pop operation. PCLATH Note: PCH 12 11 10 PCL 0 8 7 PC GOTO, CALL 2 PCLATH 11 Opcode PCLATH 4.3.1 COMPUTED GOTO A computed GOTO is accomplished by adding an offset to the program counter (ADDWF PCL). When doing a table read using a computed GOTO method, care should be exercised if the table location crosses a PCL memory boundary (each 256 word block). Refer to the application note "Implementing a Table Read" (AN556 AN556). 4.3.2 There are no instruction mnemonics called push or pop. These are actions that occur from the execution of the CALL, RETURN, RETLW, and RETFIE instructions, or the vectoring to an interrupt address. The stack operates as a circular buffer. That is, after the stack has been pushed eight times, the ninth push overwrites the value that was stored from the first push. The tenth push overwrites the second push (and so on). If the stack is effectively popped nine times, the PC value is the same as the value from the first pop. Note: There are no status bits to indicate stack overflow or stack underflow conditions. PROGRAM MEMORY PAGING The PIC16F83 PIC16F83 and PIC16CR83 PIC16CR83 have 512 words of program memory. The PIC16F84 PIC16F84 and PIC16CR84 PIC16CR84 have 1K of program memory. The CALL and GOTO instructions have an 11-bit address range. This 11-bit address range allows a branch within a 2K program memory page size. For future PIC16F8X PIC16F8X program memory expansion, there must be another two bits to specify the program memory page. These paging bits come from the PCLATH bits (Figure 4-1). When doing a CALL or a GOTO instruction, the user must ensure that these page bits (PCLATH) are programmed to the desired program memory page. If a CALL instruction (or interrupt) is executed, the entire 13-bit PC is "pushed" onto the stack (see next section). Therefore, DS30430C-page 18 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 4.5 A simple program to clear RAM locations 20h-2Fh using indirect addressing is shown in Example 4-2. Indirect Addressing; INDF and FSR Registers The INDF register is not a physical register. Addressing INDF actually addresses the register whose address is contained in the FSR register (FSR is a pointer). This is indirect addressing. EXAMPLE 4-2: EXAMPLE 4-1: NEXT INDIRECT ADDRESSING · · · · Register file 05 contains the value 10h Register file 06 contains the value 0Ah Load the value 05 into the FSR register A read of the INDF register will return the value of 10h · Increment the value of the FSR register by one (FSR = 06) · A read of the INDF register now will return the value of 0Ah. HOW TO CLEAR RAM USING INDIRECT ADDRESSING movlw movwf clrf incf btfss goto 0x20 FSR INDF FSR FSR,4 NEXT ;initialize pointer ; to RAM ;clear INDF register ;inc pointer ;all done? ;NO, clear next CONTINUE : ;YES, continue An effective 9-bit address is obtained by concatenating the 8-bit FSR register and the IRP bit (STATUS), as shown in Figure 4-1. However, IRP is not used in the PIC16F8X PIC16F8X. Reading INDF itself indirectly (FSR = 0) will produce 00h. Writing to the INDF register indirectly results in a no-operation (although STATUS bits may be affected). FIGURE 4-1: DIRECT/INDIRECT ADDRESSING Indirect Addressing Direct Addressing RP1 RP0 bank select 6 from opcode 0 IRP location select 7 bank select 00 01 10 location select not used Bank 2 0 11 not used (FSR) Bank 3 00h 00h 0Bh 0Ch Data Memory (3) Addresses map back to Bank 0 2Fh (1) 30h (1) 4Fh (2) 50h (2) 7Fh 7Fh Bank 0 Bank 1 Note 1: PIC16F83 PIC16F83 and PIC16CR83 PIC16CR83 devices. 2: PIC16F84 PIC16F84 and PIC16CR84 PIC16CR84 devices 3: For memory map detail see Figure 4-1. © 1998 Microchip Technology Inc. DS30430C-page 19 PIC16F8X PIC16F8X NOTES: DS30430C-page 20 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 5.0 I/O PORTS EXAMPLE 5-1: INITIALIZING PORTA CLRF PORTA BSF MOVLW STATUS, RP0 0x0F PORTA is a 5-bit wide latch. RA4 is a Schmitt Trigger input and an open drain output. All other RA port pins have TTL input levels and full CMOS output drivers. All pins have data direction bits (TRIS registers) which can configure these pins as output or input. MOVWF TRISA Setting a TRISA bit (=1) will make the corresponding PORTA pin an input, i.e., put the corresponding output driver in a hi-impedance mode. Clearing a TRISA bit (=0) will make the corresponding PORTA pin an output, i.e., put the contents of the output latch on the selected pin. FIGURE 5-2: The PIC16F8X PIC16F8X has two ports, PORTA and PORTB. Some port pins are multiplexed with an alternate function for other features on the device. 5.1 ; ; ; ; ; ; ; ; ; ; ; PORTA and TRISA Registers Reading the PORTA register reads the status of the pins whereas writing to it will write to the port latch. All write operations are read-modify-write operations. So a write to a port implies that the port pins are first read, then this value is modified and written to the port data latch. Data bus WR PORT Initialize PORTA by setting output data latches Select Bank 1 Value used to initialize data direction Set RA as inputs RA4 as outputs TRISA are always read as '0'. BLOCK DIAGRAM OF PIN RA4 D Q CK Q N Data Latch VSS D WR TRIS The RA4 pin is multiplexed with the TMR0 clock input. Q CK Q Schmitt Trigger input buffer TRIS Latch FIGURE 5-1: BLOCK DIAGRAM OF PINS RA3:RA0 Data bus RD TRIS D WR Port RA4 pin Q Q VDD CK Q D EN EN P RD PORT Data Latch N D WR TRIS I/O pin Q VSS CK TMR0 clock input Note: I/O pin has protection diodes to VSS only. Q TRIS Latch TTL input buffer RD TRIS Q D EN RD PORT Note: I/O pins have protection diodes to VDD and VSS. © 1998 Microchip Technology Inc. DS30430C-page 21 PIC16F8X PIC16F8X TABLE 5-1 PORTA FUNCTIONS Name Bit0 Buffer Type RA0 RA1 RA2 RA3 RA4/T0CKI bit0 bit1 bit2 bit3 bit4 Function TTL TTL TTL TTL ST Input/output Input/output Input/output Input/output Input/output or external clock input for TMR0. Output is open drain type. Legend: TTL = TTL input, ST = Schmitt Trigger input TABLE 5-2 Address SUMMARY OF REGISTERS ASSOCIATED WITH PORTA Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 05h PORTA - - - RA4/T0CKI RA3 RA2 85h TRISA - - - TRISA4 TRISA3 TRISA2 Bit 0 Value on Power-on Reset Value on all other resets RA1 RA0 -x xxxx -u uuuu TRISA1 TRISA0 -1 1111 -1 1111 Bit 1 Legend: x = unknown, u = unchanged, - = unimplemented read as '0'. Shaded cells are unimplemented, read as '0' DS30430C-page 22 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 5.2 PORTB and TRISB Registers PORTB is an 8-bit wide bi-directional port. The corresponding data direction register is TRISB. A '1' on any bit in the TRISB register puts the corresponding output driver in a hi-impedance mode. A '0' on any bit in the TRISB register puts the contents of the output latch on the selected pin(s). Each of the PORTB pins have a weak internal pull-up. A single control bit can turn on all the pull-ups. This is done by clearing the RBPU (OPTION_REG) bit. The weak pull-up is automatically turned off when the port pin is configured as an output. The pull-ups are disabled on a Power-on Reset. Four of PORTB's pins, RB7:RB4, have an interrupt on change feature. Only pins configured as inputs can cause this interrupt to occur (i.e., any RB7:RB4 pin configured as an output is excluded from the interrupt on change comparison). The pins value in input mode are compared with the old value latched on the last read of PORTB. The "mismatch" outputs of the pins are OR'ed together to generate the RB port change interrupt. FIGURE 5-3: BLOCK DIAGRAM OF PINS RB7:RB4 This interrupt can wake the device from SLEEP. The user, in the interrupt service routine, can clear the interrupt in the following manner: a) b) Read (or write) PORTB. This will end the mismatch condition. Clear flag bit RBIF. A mismatch condition will continue to set the RBIF bit. Reading PORTB will end the mismatch condition, and allow the RBIF bit to be cleared. This interrupt on mismatch feature, together with software configurable pull-ups on these four pins allow easy interface to a key pad and make it possible for wake-up on key-depression (see AN552 AN552 in the Embedded Control Handbook). Note 1: For a change on the I/O pin to be recognized, the pulse width must be at least TCY (4/fOSC) wide. The interrupt on change feature is recommended for wake-up on key depression operation and operations where PORTB is only used for the interrupt on change feature. Polling of PORTB is not recommended while using the interrupt on change feature. FIGURE 5-4: BLOCK DIAGRAM OF PINS RB3:RB0 VDD RBPU(1) VDD RBPU(1) Data bus weak P pull-up Data Latch D WR Port Q I/O pin(2) CK Data bus WR Port WR TRIS WR TRIS Q Data Latch D Q I/O pin(2) CK TRIS Latch D Q TRIS Latch D weak P pull-up TTL Input Buffer CK TTL Input Buffer CK RD TRIS Q Latch RD TRIS Q RD Port D RD Port D EN EN Set RBIF RB0/INT From other RB7:RB4 pins Q Schmitt Trigger Buffer D RD Port Note 1: TRISB = '1' enables weak pull-up (if RBPU = '0' in the OPTION_REG register). EN 2: I/O pins have diode protection to VDD and VSS. RD Port Note 1: TRISB = '1' enables weak pull-up (if RBPU = '0' in the OPTION_REG register). 2: I/O pins have diode protection to VDD and VSS. © 1998 Microchip Technology Inc. DS30430C-page 23 PIC16F8X PIC16F8X EXAMPLE 5-1: INITIALIZING PORTB CLRF PORTB BSF MOVLW STATUS, RP0 0xCF MOVWF TRISB TABLE 5-3 Name RB0/INT ; ; ; ; ; ; ; ; ; ; Initialize PORTB by setting output data latches Select Bank 1 Value used to initialize data direction Set RB as inputs RB as outputs RB as inputs PORTB FUNCTIONS Bit Buffer Type bit0 Input/output pin or external interrupt input. Internal software programmable weak pull-up. RB1 bit1 TTL Input/output pin. Internal software programmable weak pull-up. RB2 bit2 TTL Input/output pin. Internal software programmable weak pull-up. RB3 bit3 TTL Input/output pin. Internal software programmable weak pull-up. RB4 bit4 TTL Input/output pin (with interrupt on change). Internal software programmable weak pull-up. RB5 bit5 TTL Input/output pin (with interrupt on change). Internal software programmable weak pull-up. Input/output pin (with interrupt on change). Internal software programmable RB6 bit6 TTL/ST(2) weak pull-up. Serial programming clock. Input/output pin (with interrupt on change). Internal software programmable RB7 bit7 TTL/ST(2) weak pull-up. Serial programming data. Legend: TTL = TTL input, ST = Schmitt Trigger. Note 1: This buffer is a Schmitt Trigger input when configured as the external interrupt. 2: This buffer is a Schmitt Trigger input when used in serial programming mode. TABLE 5-4 Address Name TTL/ST I/O Consistency Function (1) SUMMARY OF REGISTERS ASSOCIATED WITH PORTB Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on Power-on Reset Value on all other resets uuuu uuuu 06h PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0/INT xxxx xxxx 86h TRISB TRISB7 TRISB6 TRISB5 TRISB4 TRISB3 TRISB2 TRISB1 TRISB0 1111 1111 1111 1111 81h OPTION_ REG PS0 1111 1111 1111 1111 RBPU INTEDG T0CS T0SE PSA PS2 PS1 Legend: x = unknown, u = unchanged. Shaded cells are not used by PORTB. DS30430C-page 24 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 5.3 5.3.1 5.3.2 I/O Programming Considerations SUCCESSIVE OPERATIONS ON I/O PORTS BI-DIRECTIONAL I/O PORTS Any instruction which writes, operates internally as a read followed by a write operation. The BCF and BSF instructions, for example, read the register into the CPU, execute the bit operation and write the result back to the register. Caution must be used when these instructions are applied to a port with both inputs and outputs defined. For example, a BSF operation on bit5 of PORTB will cause all eight bits of PORTB to be read into the CPU. Then the BSF operation takes place on bit5 and PORTB is written to the output latches. If another bit of PORTB is used as a bi-directional I/O pin (i.e., bit0) and it is defined as an input at this time, the input signal present on the pin itself would be read into the CPU and rewritten to the data latch of this particular pin, overwriting the previous content. As long as the pin stays in the input mode, no problem occurs. However, if bit0 is switched into output mode later on, the content of the data latch is unknown. Reading the port register, reads the values of the port pins. Writing to the port register writes the value to the port latch. When using read-modify-write instructions (i.e., BCF, BSF, etc.) on a port, the value of the port pins is read, the desired operation is done to this value, and this value is then written to the port latch. A pin actively outputting a Low or High should not be driven from external devices at the same time in order to change the level on this pin ("wired-or", "wired-and"). The resulting high output current may damage the chip. FIGURE 5-5: Example 5-1 shows the effect of two sequential read-modify-write instructions (e.g., BCF, BSF, etc.) on an I/O port. EXAMPLE 5-1: READ-MODIFY-WRITE INSTRUCTIONS ON AN I/O PORT ;Initial PORT settings: PORTB Inputs ; PORTB Outputs ;PORTB have external pull-ups and are ;not connected to other circuitry ; ; PORT latch PORT pins ; - -BCF PORTB, 7 ; 01pp ppp 11pp ppp BCF PORTB, 6 ; 10pp ppp 11pp ppp BSF STATUS, RP0 ; BCF TRISB, 7 ; 10pp ppp 11pp ppp BCF TRISB, 6 ; 10pp ppp 10pp ppp ; ;Note that the user may have expected the ;pin values to be 00pp ppp. The 2nd BCF ;caused RB7 to be latched as the pin value ;(high). SUCCESSIVE I/O OPERATION Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 PC Instruction fetched The actual write to an I/O port happens at the end of an instruction cycle, whereas for reading, the data must be valid at the beginning of the instruction cycle (Figure 5-5). Therefore, care must be exercised if a write followed by a read operation is carried out on the same I/O port. The sequence of instructions should be such that the pin voltage stabilizes (load dependent) before the next instruction which causes that file to be read into the CPU is executed. Otherwise, the previous state of that pin may be read into the CPU rather than the new state. When in doubt, it is better to separate these instructions with a NOP or another instruction not accessing this I/O port. PC Q1 Q2 Q3 Q4 PC + 2 PC + 3 NOP PC + 1 MOVWF PORTB MOVF PORTB,W write to PORTB NOP This example shows a write to PORTB followed by a read from PORTB. Note that: data setup time = (0.25TCY 25TCY - TPD) RB7:RB0 where TCY = instruction cycle TPD = propagation delay Port pin sampled here TPD Instruction executed NOP MOVWF PORTB write to PORTB © 1998 Microchip Technology Inc. Note: MOVF PORTB,W Therefore, at higher clock frequencies, a write followed by a read may be problematic. DS30430C-page 25 PIC16F8X PIC16F8X NOTES: DS30430C-page 26 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 6.0 TIMER0 MODULE AND TMR0 REGISTER edge select bit, T0SE (OPTION_REG). Clearing bit T0SE selects the rising edge. Restrictions on the external clock input are discussed in detail in Section 6.2. The Timer0 module timer/counter has the following features: · · · · · · The prescaler is shared between the Timer0 Module and the Watchdog Timer. The prescaler assignment is controlled, in software, by control bit PSA (OPTION_REG). Clearing bit PSA will assign the prescaler to the Timer0 Module. The prescaler is not readable or writable. When the prescaler (Section 6.3) is assigned to the Timer0 Module, the prescale value (1:2, 1:4, ., 1:256) is software selectable. 8-bit timer/counter Readable and writable 8-bit software programmable prescaler Internal or external clock select Interrupt on overflow from FFh to 00h Edge select for external clock 6.1 Timer mode is selected by clearing the T0CS bit (OPTION_REG). In timer mode, the Timer0 module (Figure 6-1) will increment every instruction cycle (without prescaler). If the TMR0 register is written, the increment is inhibited for the following two cycles (Figure 6-2 and Figure 6-3). The user can work around this by writing an adjusted value to the TMR0 register. The TMR0 interrupt is generated when the TMR0 register overflows from FFh to 00h. This overflow sets the T0IF bit (INTCON). The interrupt can be masked by clearing enable bit T0IE (INTCON). The T0IF bit must be cleared in software by the Timer0 Module interrupt service routine before re-enabling this interrupt. The TMR0 interrupt (Figure 6-4) cannot wake the processor from SLEEP since the timer is shut off during SLEEP. Counter mode is selected by setting the T0CS bit (OPTION_REG). In this mode TMR0 will increment either on every rising or falling edge of pin RA4/T0CKI. The incrementing edge is determined by the T0 source FIGURE 6-1: TMR0 Interrupt TMR0 BLOCK DIAGRAM Data bus FOSC/4 0 PSout 1 Sync with Internal clocks 1 RA4/T0CKI pin Programmable Prescaler 8 0 TMR0 register PSout (2 cycle delay) T0SE 3 PS2, PS1, PS0 Set bit T0IF on Overflow PSA T0CS Note 1: Bits T0CS, T0SE, PS2, PS1, PS0 and PSA are located in the OPTION_REG register. 2: The prescaler is shared with the Watchdog Timer (Figure 6-6) FIGURE 6-2: TMR0 TIMING: INTERNAL CLOCK/NO PRESCALER Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 PC-1 PC TMR0 PC MOVWF TMR0 Instruction Fetch T0 T0+1 Instruction Executed © 1998 Microchip Technology Inc. PC+1 PC+2 PC+3 MOVF TMR0,W MOVF TMR0,W MOVF TMR0,W T0+2 NT0 NT0 Write TMR0 executed Read TMR0 reads NT0 Read TMR0 reads NT0 PC+4 MOVF TMR0,W NT0 Read TMR0 reads NT0 PC+5 PC+6 MOVF TMR0,W NT0+1 Read TMR0 reads NT0 + 1 NT0+2 T0 Read TMR0 reads NT0 + 2 DS30430C-page 27 PIC16F8X PIC16F8X FIGURE 6-3: TMR0 TIMING: INTERNAL CLOCK/PRESCALE 1:2 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 PC-1 PC Instruction Fetch PC+1 MOVWF TMR0 PC MOVF TMR0,W PC+3 T0+1 T0 TMR0 PC+2 Instruction Execute PC+5 MOVF TMR0,W PC+6 MOVF TMR0,W NT0+1 NT0 Write TMR0 executed FIGURE 6-4: PC+4 MOVF TMR0,W MOVF TMR0,W Read TMR0 reads NT0 Read TMR0 reads NT0 Read TMR0 reads NT0 Read TMR0 reads NT0 Read TMR0 reads NT0 + 1 TMR0 INTERRUPT TIMING Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 OSC1 CLKOUT(3) TMR0 timer FEh T0IF bit 4 (INTCON) 1 FFh 00h 01h 02h 1 GIE bit (INTCON) Interrupt Latency(2) INSTRUCTION FLOW PC PC Instruction fetched Inst (PC) Instruction executed Inst (PC-1) PC +1 PC +1 Inst (PC) Dummy cycle 0005h Inst (0004h) Inst (PC+1) 0004h Inst (0005h) Dummy cycle Inst (0004h) Note 1: T0IF interrupt flag is sampled here (every Q1). 2: Interrupt latency = 3.25Tcy, where Tcy = instruction cycle time. 3: CLKOUT is available only in RC oscillator mode. 4: The timer clock (after the synchronizer circuit) which increments the timer from FFh to 00h immediately sets the T0IF bit. The TMR0 register will roll over 3 Tosc cycles later. DS30430C-page 28 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 6.2 Using TMR0 with External Clock 6.2.2 TMR0 INCREMENT DELAY When an external clock input is used for TMR0, it must meet certain requirements. The external clock requirement is due to internal phase clock (TOSC) synchronization. Also, there is a delay in the actual incrementing of the TMR0 register after synchronization. Since the prescaler output is synchronized with the internal clocks, there is a small delay from the time the external clock edge occurs to the time the Timer0 Module is actually incremented. Figure 6-5 shows the delay from the external clock edge to the timer incrementing. 6.2.1 6.3 EXTERNAL CLOCK SYNCHRONIZATION Prescaler When no prescaler is used, the external clock input is the same as the prescaler output. The synchronization of pin RA4/T0CKI with the internal phase clocks is accomplished by sampling the prescaler output on the Q2 and Q4 cycles of the internal phase clocks (Figure 6-5). Therefore, it is necessary for T0CKI to be high for at least 2Tosc (plus a small RC delay) and low for at least 2Tosc (plus a small RC delay). Refer to the electrical specification of the desired device. An 8-bit counter is available as a prescaler for the Timer0 Module, or as a postscaler for the Watchdog Timer (Figure 6-6). For simplicity, this counter is being referred to as "prescaler" throughout this data sheet. Note that there is only one prescaler available which is mutually exclusive between the Timer0 Module and the Watchdog Timer. Thus, a prescaler assignment for the Timer0 Module means that there is no prescaler for the Watchdog Timer, and vice-versa. When a prescaler is used, the external clock input is divided by an asynchronous ripple counter type prescaler so that the prescaler output is symmetrical. For the external clock to meet the sampling requirement, the ripple counter must be taken into account. Therefore, it is necessary for T0CKI to have a period of at least 4Tosc (plus a small RC delay) divided by the prescaler value. The only requirement on T0CKI high and low time is that they do not violate the minimum pulse width requirement of 10 ns. Refer to parameters 40, 41 and 42 in the AC Electrical Specifications of the desired device. The PSA and PS2:PS0 bits (OPTION_REG) determine the prescaler assignment and prescale ratio. © 1998 Microchip Technology Inc. When assigned to the Timer0 Module, all instructions writing to the Timer0 Module (e.g., CLRF 1, MOVWF 1, BSF 1,x .etc.) will clear the prescaler. When assigned to WDT, a CLRWDT instruction will clear the prescaler along with the Watchdog Timer. The prescaler is not readable or writable. DS30430C-page 29 PIC16F8X PIC16F8X FIGURE 6-5: TIMER0 TIMING WITH EXTERNAL CLOCK Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Ext. Clock Input or Prescaler Out (Note 2) (Note 3) Ext. Clock/Prescaler Output After Sampling Increment TMR0 (Q4) TMR0 T0 T0 + 1 T0 + 2 Note 1: Delay from clock input change to TMR0 increment is 3Tosc to 7Tosc. (Duration of Q = Tosc). Therefore, the error in measuring the interval between two edges on TMR0 input = ± 4Tosc max. 2: External clock if no prescaler selected, Prescaler output otherwise. 3: The arrows indicate where sampling occurs. A small clock pulse may be missed by sampling. FIGURE 6-6: BLOCK DIAGRAM OF THE TMR0/WDT PRESCALER Data Bus CLKOUT (= Fosc/4) 0 RA4/T0CKI pin M U X 8 1 M U X 0 1 SYNC 2 Cycles TMR0 register T0SE T0CS 0 Watchdog Timer 1 M U X Set bit T0IF on overflow PSA 8-bit Prescaler 8 8 - to - 1MUX PS2:PS0 PSA WDT Enable bit 1 0 MUX PSA WDT time-out Note: T0CS, T0SE, PSA, PS2:PS0 are bits in the OPTION_REG register. DS30430C-page 30 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 6.3.1 SWITCHING PRESCALER ASSIGNMENT EXAMPLE 6-1: The prescaler assignment is fully under software control (i.e., it can be changed "on the fly" during program execution). Note: To avoid an unintended device RESET, the following instruction sequence (Example 6-1) must be executed when changing the prescaler assignment from Timer0 to the WDT. This sequence must be taken even if the WDT is disabled. To change prescaler from the WDT to the Timer0 module use the sequence shown in Example 6-2. CHANGING PRESCALER (TIMER0WDT) BCF CLRF STATUS, RP0 TMR0 BSF CLRWDT MOVLW MOVWF BCF STATUS, RP0 b'xxxx1xxx' OPTION_REG STATUS, RP0 EXAMPLE 6-2: CHANGING PRESCALER (WDTTIMER0) CLRWDT BSF MOVLW Address STATUS, RP0 b'xxxx0xxx' MOVWF BCF TABLE 6-1 ;Bank 0 ;Clear TMR0 ; and Prescaler ;Bank 1 ;Clears WDT ;Select new ; prescale value ;Bank 0 OPTION_REG STATUS, RP0 ;Clear WDT and ; prescaler ;Bank 1 ;Select TMR0, new ; prescale value ' and clock source ; ;Bank 0 REGISTERS ASSOCIATED WITH TIMER0 Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 1 Bit 0 Timer0 module's register Value on Power-on Reset Value on all other resets xxxx xxxx Bit 2 uuuu uuuu 01h TMR0 0Bh INTCON GIE EEIE T0IE INTE RBIE T0IF INTF RBIF 0000 000x 0000 0000 81h OPTION_ REG RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 1111 1111 85h TRISA - - - TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 -1 1111 -1 1111 Legend: x = unknown, u = unchanged. - = unimplemented read as '0'. Shaded cells are not associated with Timer0. © 1998 Microchip Technology Inc. DS30430C-page 31 PIC16F8X PIC16F8X NOTES: DS30430C-page 32 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 7.0 DATA EEPROM MEMORY The EEPROM data memory is readable and writable during normal operation (full VDD range). This memory is not directly mapped in the register file space. Instead it is indirectly addressed through the Special Function Registers. There are four SFRs used to read and write this memory. These registers are: · · · · EECON1 EECON2 EEDATA EEADR data memory is rated for high erase/write cycles. The write time is controlled by an on-chip timer. The writetime will vary with voltage and temperature as well as from chip to chip. Please refer to AC specifications for exact limits. When the device is code protected, the CPU may continue to read and write the data EEPROM memory. The device programmer can no longer access this memory. 7.1 EEDATA holds the 8-bit data for read/write, and EEADR holds the address of the EEPROM location being accessed. PIC16F8X PIC16F8X devices have 64 bytes of data EEPROM with an address range from 0h to 3Fh. The EEPROM data memory allows byte read and write. A byte write automatically erases the location and writes the new data (erase before write). The EEPROM FIGURE 7-1: EEADR The EEADR register can address up to a maximum of 256 bytes of data EEPROM. Only the first 64 bytes of data EEPROM are implemented. The upper two bits are address decoded. This means that these two bits must always be '0' to ensure that the address is in the 64 byte memory space. EECON1 REGISTER (ADDRESS 88h) U U U R/W-0 R/W-x R/W-0 R/S-0 R/S-x - - - EEIF WRERR WREN WR RD bit7 bit0 R W S U = Readable bit = Writable bit = Settable bit = Unimplemented bit, read as `0' - n = Value at POR reset bit 7:5 Unimplemented: Read as '0' bit 4 EEIF: EEPROM Write Operation Interrupt Flag bit 1 = The write operation completed (must be cleared in software) 0 = The write operation is not complete or has not been started bit 3 WRERR: EEPROM Error Flag bit 1 = A write operation is prematurely terminated (any MCLR reset or any WDT reset during normal operation) 0 = The write operation completed bit 2 WREN: EEPROM Write Enable bit 1 = Allows write cycles 0 = Inhibits write to the data EEPROM bit 1 WR: Write Control bit 1 = initiates a write cycle. (The bit is cleared by hardware once write is complete. The WR bit can only be set (not cleared) in software. 0 = Write cycle to the data EEPROM is complete bit 0 RD: Read Control bit 1 = Initiates an EEPROM read (read takes one cycle. RD is cleared in hardware. The RD bit can only be set (not cleared) in software). 0 = Does not initiate an EEPROM read © 1998 Microchip Technology Inc. DS30430C-page 33 PIC16F8X PIC16F8X EECON1 and EECON2 Registers EECON1 is the control register with five low order bits physically implemented. The upper-three bits are nonexistent and read as '0's. Control bits RD and WR initiate read and write, respectively. These bits cannot be cleared, only set, in software. They are cleared in hardware at completion of the read or write operation. The inability to clear the WR bit in software prevents the accidental, premature termination of a write operation. The WREN bit, when set, will allow a write operation. On power-up, the WREN bit is clear. The WRERR bit is set when a write operation is interrupted by a MCLR reset or a WDT time-out reset during normal operation. In these situations, following reset, the user can check the WRERR bit and rewrite the location. The data and address will be unchanged in the EEDATA and EEADR registers. Interrupt flag bit EEIF is set when write is complete. It must be cleared in software. EECON2 is not a physical register. Reading EECON2 will read all '0's. The EECON2 register is used exclusively in the Data EEPROM write sequence. 7.3 Reading the EEPROM Data Memory To read a data memory location, the user must write the address to the EEADR register and then set control bit RD (EECON1). The data is available, in the very next cycle, in the EEDATA register; therefore it can be read in the next instruction. EEDATA will hold this value until another read or until it is written to by the user (during a write operation). EXAMPLE 7-1: BCF MOVLW MOVWF BSF BSF BCF MOVF DATA EEPROM READ STATUS, RP0 CONFIG_ADDR EEADR STATUS, RP0 EECON1, RD STATUS, RP0 EEDATA, W DS30430C-page 34 ; ; ; ; ; ; ; Bank 0 7.4 Writing to the EEPROM Data Memory To write an EEPROM data location, the user must first write the address to the EEADR register and the data to the EEDATA register. Then the user must follow a specific sequence to initiate the write for each byte. EXAMPLE 7-1: DATA EEPROM WRITE BSF BCF BSF MOVLW MOVWF MOVLW MOVWF BSF STATUS, RP0 INTCON, GIE EECON1, WREN 55h EECON2 AAh EECON2 EECON1,WR BSF Required Sequence 7.2 INTCON, GIE ; ; ; ; ; ; ; ; ; ; Bank 1 Disable INTs. Enable Write Write 55h Write AAh Set WR bit begin write Enable INTs. The write will not initiate if the above sequence is not exactly followed (write 55h to EECON2, write AAh to EECON2, then set WR bit) for each byte. We strongly recommend that interrupts be disabled during this code segment. Additionally, the WREN bit in EECON1 must be set to enable write. This mechanism prevents accidental writes to data EEPROM due to errant (unexpected) code execution (i.e., lost programs). The user should keep the WREN bit clear at all times, except when updating EEPROM. The WREN bit is not cleared by hardware After a write sequence has been initiated, clearing the WREN bit will not affect this write cycle. The WR bit will be inhibited from being set unless the WREN bit is set. At the completion of the write cycle, the WR bit is cleared in hardware and the EE Write Complete Interrupt Flag bit (EEIF) is set. The user can either enable this interrupt or poll this bit. EEIF must be cleared by software. Address to read Bank 1 EE Read Bank 0 W = EEDATA © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 7.5 Write Verify SUBWF EEDATA, W BTFSS STATUS, Z GOTO WRITE_ERR : : Depending on the application, good programming practice may dictate that the value written to the Data EEPROM should be verified (Example 7-1) to the desired value to be written. This should be used in applications where an EEPROM bit will be stressed near the specification limit. The Total Endurance disk will help determine your comfort level. 7.6 WRITE VERIFY BCF : : MOVF BSF STATUS, RP0 ; ; ; EEDATA, W ; STATUS, RP0 ; BSF EECON1, RD Bank 0 Any code can go here 7.7 Must be in Bank 0 Bank 1 Data EEPROM Operation during Code Protect When the device is code protected, the CPU is able to read and write unscrambled data to the Data EEPROM. ; YES, Read the ; value written STATUS, RP0 ; Bank 0 BCF ; ; Is the value written (in W reg) and ; read (in EEDATA) the same? ; Address Protection Against Spurious Writes The write initiate sequence and the WREN bit together help prevent an accidental write during brown-out, power glitch, or software malfunction. READ TABLE 7-1 Is difference 0? NO, Write error YES, Good write Continue program There are conditions when the device may not want to write to the data EEPROM memory. To protect against spurious EEPROM writes, various mechanisms have been built in. On power-up, WREN is cleared. Also, the Power-up Timer (72 ms duration) prevents EEPROM write. Generally the EEPROM write failure will be a bit which was written as a '1', but reads back as a '0' (due to leakage off the bit). EXAMPLE 7-1: ; ; ; ; ; For ROM devices, there are two code protection bits (Section 8.1). One for the ROM program memory and one for the Data EEPROM memory. REGISTERS/BITS ASSOCIATED WITH DATA EEPROM Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Value on Power-on Reset Value on all other resets 08h EEDATA EEPROM data register xxxx xxxx uuuu uuuu 09h EEADR EEPROM address register xxxx xxxx uuuu uuuu -0 x000 -0 q000 - - - - 88h EECON1 89h EECON2 - - - EEPROM control register 2 EEIF WRERR WREN WR RD Legend: x = unknown, u = unchanged, - = unimplemented read as '0', q = value depends upon condition. Shaded cells are not used by Data EEPROM. © 1998 Microchip Technology Inc. DS30430C-page 35 PIC16F8X PIC16F8X NOTES: DS30430C-page 36 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 8.0 SPECIAL FEATURES OF THE CPU What sets a microcontroller apart from other processors are special circuits to deal with the needs of real time applications. The PIC16F8X PIC16F8X has a host of such features intended to maximize system reliability, minimize cost through elimination of external components, provide power saving operating modes and offer code protection. These features are: · OSC Selection · Reset - Power-on Reset (POR) - Power-up Timer (PWRT) - Oscillator Start-up Timer (OST) · Interrupts · Watchdog Timer (WDT) · SLEEP · Code protection · ID locations · In-circuit serial programming The PIC16F8X PIC16F8X has a Watchdog Timer which can be shut off only through configuration bits. It runs off its own RC oscillator for added reliability. There are two timers that offer necessary delays on power-up. One is the Oscillator Start-up Timer (OST), intended to keep the chip in reset until the crystal oscillator is stable. The other is the Power-up Timer (PWRT), which provides a fixed delay of 72 ms (nominal) on power-up only. This design keeps the device in reset while the power supply stabilizes. With these two timers on-chip, most applications need no external reset circuitry. SLEEP mode offers a very low current power-down mode. The user can wake-up from SLEEP through external reset, Watchdog Timer time-out or through an interrupt. Several oscillator options are provided to allow the part to fit the application. The RC oscillator option saves system cost while the LP crystal option saves power. A set of configuration bits are used to select the various options. © 1998 Microchip Technology Inc. DS30430C-page 37 PIC16F8X PIC16F8X 8.1 Configuration Bits The configuration bits can be programmed (read as '0') or left unprogrammed (read as '1') to select various device configurations. These bits are mapped in program memory location 2007h. FIGURE 8-1: Address 2007h is beyond the user program memory space and it belongs to the special test/configuration memory space (2000h - 3FFFh). This space can only be accessed during programming. To find out how to program the PIC16C84 PIC16C84, refer to PIC16C84 PIC16C84 EEPROM Memory Programming Specification (DS30189 DS30189). CONFIGURATION WORD - PIC16CR83 PIC16CR83 AND PIC16CR84 PIC16CR84 R-u R-u R-u R-u R-u R-u R/P-u R-u R-u R-u CP CP CP CP CP CP DP CP CP CP bit13 R-u R-u R-u R-u PWRTE WDTE FOSC1 FOSC0 bit0 R = Readable bit P = Programmable bit - n = Value at POR reset u = unchanged bit 13:8 CP: Program Memory Code Protection bit 1 = Code protection off 0 = Program memory is code protected bit 7 DP: Data Memory Code Protection bit 1 = Code protection off 0 = Data memory is code protected bit 6:4 CP: Program Memory Code Protection bit 1 = Code protection off 0 = Program memory is code protected bit 3 PWRTE: Power-up Timer Enable bit 1 = Power-up timer is disabled 0 = Power-up timer is enabled bit 2 WDTE: Watchdog Timer Enable bit 1 = WDT enabled 0 = WDT disabled bit 1:0 FOSC1:FOSC0: Oscillator Selection bits 11 = RC oscillator 10 = HS oscillator 01 = XT oscillator 00 = LP oscillator DS30430C-page 38 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X FIGURE 8-2: CONFIGURATION WORD - PIC16F83 PIC16F83 AND PIC16F84 PIC16F84 R/P-u R/P-u R/P-u R/P-u R/P-u R/P-u R/P-u R/P-u CP CP CP CP CP CP CP CP R/P-u R/P-u CP CP R/P-u R/P-u R/P-u R/P-u PWRTE WDTE FOSC1 FOSC0 bit13 bit0 R = Readable bit P = Programmable bit - n = Value at POR reset u = unchanged bit 13:4 CP: Code Protection bit 1 = Code protection off 0 = All memory is code protected bit 3 PWRTE: Power-up Timer Enable bit 1 = Power-up timer is disabled 0 = Power-up timer is enabled bit 2 WDTE: Watchdog Timer Enable bit 1 = WDT enabled 0 = WDT disabled bit 1:0 FOSC1:FOSC0: Oscillator Selection bits 11 = RC oscillator 10 = HS oscillator 01 = XT oscillator 00 = LP oscillator 8.2 Oscillator Configurations 8.2.1 FIGURE 8-3: OSCILLATOR TYPES The PIC16F8X PIC16F8X can be operated in four different oscillator modes. The user can program two configuration bits (FOSC1 and FOSC0) to select one of these four modes: · · · · LP XT HS RC 8.2.2 Low Power Crystal Crystal/Resonator High Speed Crystal/Resonator Resistor/Capacitor CRYSTAL OSCILLATOR / CERAMIC RESONATORS In XT, LP or HS modes a crystal or ceramic resonator is connected to the OSC1/CLKIN and OSC2/CLKOUT pins to establish oscillation (Figure 8-3). CRYSTAL/CERAMIC RESONATOR OPERATION (HS, XT OR LP OSC CONFIGURATION) C1(1) OSC1 XTAL RF(3) OSC2 RS(2) C2(1) Note1: 2: 3: To internal logic SLEEP PIC16FXX PIC16FXX See Table 8-1 for recommended values of C1 and C2. A series resistor (RS) may be required for AT strip cut crystals. RF varies with the crystal chosen. The PIC16F8X PIC16F8X oscillator design requires the use of a parallel cut crystal. Use of a series cut crystal may give a frequency out of the crystal manufacturers specifications. When in XT, LP or HS modes, the device can have an external clock source to drive the OSC1/CLKIN pin (Figure 8-4). © 1998 Microchip Technology Inc. DS30430C-page 39 PIC16F8X PIC16F8X FIGURE 8-4: EXTERNAL CLOCK INPUT OPERATION (HS, XT OR LP OSC CONFIGURATION) OSC1 Clock from ext. system PIC16FXX PIC16FXX Open TABLE 8-1 OSC2 CAPACITOR SELECTION FOR CERAMIC RESONATORS Ranges Tested: Mode Freq XT 455 kHz 2.0 MHz 4.0 MHz 8.0 MHz 10.0 MHz HS Note : OSC1/C1 OSC2/C2 47 - 100 pF 47 - 100 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF Recommended values of C1 and C2 are identical to the ranges tested table. Higher capacitance increases the stability of the oscillator but also increases the start-up time. These values are for design guidance only. Since each resonator has its own characteristics, the user should consult the resonator manufacturer for the appropriate values of external components. Crystals Tested: 32.768 kHz 100 kHz 200 kHz 1.0 MHz 2.0 MHz 4.0 MHz 10.0 MHz 8.2.3 Epson C-001R32 C-001R32.768K-A 768K-A Epson C-2 100.00 KC-P STD XTL 200.000 KHz ECS ECS-10-13-2 ECS-10-13-2 ECS ECS-20-S-2 ECS-20-S-2 ECS ECS-40-S-4 ECS-40-S-4 ECS ECS-100-S-4 ECS-100-S-4 ± 20 PPM ± 20 PPM ± 20 PPM ± 50 PPM ± 50 PPM ± 50 PPM ± 50 PPM EXTERNAL CRYSTAL OSCILLATOR CIRCUIT Either a prepackaged oscillator can be used or a simple oscillator circuit with TTL gates can be built. Prepackaged oscillators provide a wide operating range and better stability. A well-designed crystal oscillator will provide good performance with TTL gates. Two types of crystal oscillator circuits are available; one with series resonance, and one with parallel resonance. Figure 8-5 shows a parallel resonant oscillator circuit. The circuit is designed to use the fundamental frequency of the crystal. The 74AS04 74AS04 inverter performs the 180-degree phase shift that a parallel oscillator requires. The 4.7 k resistor provides negative feedback for stability. The 10 k potentiometer biases the 74AS04 74AS04 in the linear region. This could be used for external oscillator designs. Resonators Tested: 455 kHz 2.0 MHz 4.0 MHz 8.0 MHz 10.0 MHz Panasonic EFO-A455K04B EFO-A455K04B Murata Erie CSA2.00MG Murata Erie CSA4.00MG Murata Erie CSA8.00MT Murata Erie CSA10 CSA10.00MTZ 00MTZ ± 0.3% ± 0.5% ± 0.5% ± 0.5% ± 0.5% FIGURE 8-5: EXTERNAL PARALLEL RESONANT CRYSTAL OSCILLATOR CIRCUIT +5V To Other Devices 10k None of the resonators had built-in capacitors. 4.7k TABLE 8-2 CAPACITOR SELECTION FOR CRYSTAL OSCILLATOR Mode Freq OSC1/C1 32 kHz 200 kHz 100 kHz 2 MHz 4 MHz 4 MHz 10 MHz 68 - 100 pF 15 - 33 pF 100 - 150 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF 68 - 100 pF 15 - 33 pF 100 - 150 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF 15 - 33 pF CLKIN 74AS04 74AS04 OSC2/C2 LP XT HS Note : Higher capacitance increases the stability of oscillator but also increases the start-up time. These values are for design guidance only. Rs may be required in HS mode as well as XT mode to avoid overdriving crystals with low drive level specification. Since each crystal has its own characteristics, the user should consult the crystal manufacturer for appropriate values of external components. PIC16FXX PIC16FXX 74AS04 74AS04 10k XTAL 10k 20 pF 20 pF Figure 8-6 shows a series resonant oscillator circuit. This circuit is also designed to use the fundamental frequency of the crystal. The inverter performs a 180-degree phase shift. The 330 k resistors provide the negative feedback to bias the inverters in their linear region. For VDD > 4.5V, C1 = C2 30 pF is recommended. DS30430C-page 40 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X FIGURE 8-6: EXTERNAL SERIES RESONANT CRYSTAL OSCILLATOR CIRCUIT FIGURE 8-7: RC OSCILLATOR MODE VDD Rext 330 k 330 k 74AS04 74AS04 74AS04 74AS04 To Other Devices PIC16FXX PIC16FXX Cext 74AS04 74AS04 CLKIN Fosc/4 Recommended values: XTAL Note: RC OSCILLATOR For timing insensitive applications the RC device option offers additional cost savings. The RC oscillator frequency is a function of the supply voltage, the resistor (Rext) values, capacitor (Cext) values, and the operating temperature. In addition to this, the oscillator frequency will vary from unit to unit due to normal process parameter variation. Furthermore, the difference in lead frame capacitance between package types also affects the oscillation frequency, especially for low Cext values. The user needs to take into account variation due to tolerance of the external R and C components. Figure 8-7 shows how an R/C combination is connected to the PIC16F8X PIC16F8X. For Rext values below 4 k, the oscillator operation may become unstable, or stop completely. For very high Rext values (e.g., 1 M), the oscillator becomes sensitive to noise, humidity and leakage. Thus, we recommend keeping Rext between 5 k and 100 k. Although the oscillator will operate with no external capacitor (Cext = 0 pF), we recommend using values above 20 pF for noise and stability reasons. With little or no external capacitance, the oscillation frequency can vary dramatically due to changes in external capacitances, such as PCB trace capacitance or package lead frame capacitance. See the electrical specification section for RC frequency variation from part to part due to normal process variation. The variation is larger for larger R (since leakage current variation will affect RC frequency more for large R) and for smaller C (since variation of input capacitance has a greater affect on RC frequency). PIC16FXX PIC16FXX VSS 0.1 µF 8.2.4 Internal clock OSC1 8.3 OSC2/CLKOUT 5 k Rext 100 k Cext > 20pF When the device oscillator is in RC mode, do not drive the OSC1 pin with an external clock or you may damage the device. Reset The PIC16F8X PIC16F8X differentiates between various kinds of reset: · · · · · Power-on Reset (POR) MCLR reset during normal operation MCLR reset during SLEEP WDT Reset (during normal operation) WDT Wake-up (during SLEEP) Figure 8-8 shows a simplified block diagram of the on-chip reset circuit. The MCLR reset path has a noise filter to ignore small pulses. The electrical specifications state the pulse width requirements for the MCLR pin. Some registers are not affected in any reset condition; their status is unknown on a POR reset and unchanged in any other reset. Most other registers are reset to a "reset state" on POR, MCLR or WDT reset during normal operation and on MCLR reset during SLEEP. They are not affected by a WDT reset during SLEEP, since this reset is viewed as the resumption of normal operation. Table 8-3 gives a description of reset conditions for the program counter (PC) and the STATUS register. Table 8-4 gives a full description of reset states for all registers. The TO and PD bits are set or cleared differently in different reset situations (Section 8.7). These bits are used in software to determine the nature of the reset. See the electrical specification section for variation of oscillator frequency due to VDD for given Rext/Cext values as well as frequency variation due to operating temperature. The oscillator frequency, divided by 4, is available on the OSC2/CLKOUT pin, and can be used for test purposes or to synchronize other logic (see Figure 3-2 for waveform). © 1998 Microchip Technology Inc. DS30430C-page 41 PIC16F8X PIC16F8X FIGURE 8-8: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT External Reset MCLR WDT Module SLEEP WDT Time_Out Reset VDD rise detect Power_on_Reset S 10-bit Ripple counter R VDD OST/PWRT OST Chip_Reset Q OSC1/ CLKIN PWRT On-chip RC OSC(1) 10-bit Ripple counter Enable PWRT Note 1: This is a separate oscillator from the RC oscillator of the CLKIN pin. DS30430C-page 42 See Table 8-5 Enable OST © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X TABLE 8-3 RESET CONDITION FOR PROGRAM COUNTER AND THE STATUS REGISTER Program Counter Condition STATUS Register Power-on Reset 000h 0001 1xxx MCLR Reset during normal operation 000h 000u uuuu MCLR Reset during SLEEP 000h 0001 0uuu WDT Reset (during normal operation) 000h 0000 1uuu WDT Wake-up PC + 1 Interrupt wake-up from SLEEP PC + 1 uuu0 0uuu (1) uuu1 0uuu Legend: u = unchanged, x = unknown. Note 1: When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt vector (0004h). TABLE 8-4 Register W RESET CONDITIONS FOR ALL REGISTERS Address Power-on Reset MCLR Reset during: ­ normal operation ­ SLEEP WDT Reset during normal operation Wake-up from SLEEP: ­ through interrupt ­ through WDT Time-out - xxxx xxxx uuuu uuuu uuuu uuuu INDF 00h - - - - - - TMR0 01h xxxx xxxx uuuu uuuu uuuu uuuu PCL 02h 0000h 0000h STATUS 03h 0001 1xxx 000q quuu(3) uuuq quuu(3) FSR 04h xxxx xxxx uuuu uuuu uuuu uuuu PORTA 05h -x xxxx -u uuuu -u uuuu PORTB 06h xxxx xxxx uuuu uuuu uuuu uuuu EEDATA 08h xxxx xxxx uuuu uuuu uuuu uuuu EEADR 09h xxxx xxxx uuuu uuuu uuuu uuuu PCLATH 0Ah -0 0000 -0 0000 -u uuuu INTCON 0Bh 0000 000x 0000 000u uuuu uuuu(1) INDF 80h - - - - - - OPTION_REG 81h 1111 1111 1111 1111 uuuu uuuu PCL 82h 0000h 0000h PC + 1(2) PC + 1 (3) uuuq quuu(3) STATUS 83h 0001 1xxx 000q quuu FSR 84h xxxx xxxx uuuu uuuu uuuu uuuu TRISA 85h -1 1111 -1 1111 -u uuuu TRISB 86h 1111 1111 1111 1111 uuuu uuuu EECON1 88h -0 x000 -0 q000 -0 uuuu EECON2 89h - - - - - - PCLATH 8Ah -0 0000 -0 0000 -u uuuu INTCON 8Bh 0000 000x 0000 000u uuuu uuuu(1) Legend: u = unchanged, x = unknown, - = unimplemented bit read as '0', q = value depends on condition. Note 1: One or more bits in INTCON will be affected (to cause wake-up). 2: When the wake-up is due to an interrupt and the GIE bit is set, the PC is loaded with the interrupt vector (0004h). 3: Table 8-3 lists the reset value for each specific condition. © 1998 Microchip Technology Inc. DS30430C-page 43 PIC16F8X PIC16F8X 8.4 Power-on Reset (POR) A Power-on Reset pulse is generated on-chip when VDD rise is detected (in the range of 1.2V - 1.7V). To take advantage of the POR, just tie the MCLR pin directly (or through a resistor) to VDD. This will eliminate external RC components usually needed to create Power-on Reset. A minimum rise time for VDD must be met for this to operate properly. See Electrical Specifications for details. When the device starts normal operation (exits the reset condition), device operating parameters (voltage, frequency, temperature, .) must be meet to ensure operation. If these conditions are not met, the device must be held in reset until the operating conditions are met. For additional information, refer to Application Note AN607 AN607, "Power-up Trouble Shooting." The POR circuit does not produce an internal reset when VDD declines. 8.5 Power-up Timer (PWRT) The Power-up Timer (PWRT) provides a fixed 72 ms nominal time-out (TPWRT) from POR (Figure 8-10, Figure 8-11, Figure 8-12 and Figure 8-13). The Power-up Timer operates on an internal RC oscillator. The chip is kept in reset as long as the PWRT is active. The PWRT delay allows the VDD to rise to an acceptable level (Possible exception shown in Figure 8-13). FIGURE 8-9: EXTERNAL POWER-ON RESET CIRCUIT (FOR SLOW VDD POWER-UP) VDD VDD D R R1 MCLR C PIC16FXX PIC16FXX Note 1: External Power-on Reset circuit is required only if VDD power-up rate is too slow. The diode D helps discharge the capacitor quickly when VDD powers down. 2: R < 40 k is recommended to make sure that voltage drop across R does not exceed 0.2V (max leakage current spec on MCLR pin is 5 µA). A larger voltage drop will degrade VIH level on the MCLR pin. 3: R1 = 100 to 1 k will limit any current flowing into MCLR from external capacitor C in the event of an MCLR pin breakdown due to ESD or EOS. A configuration bit, PWRTE, can enable/disable the PWRT. See either Figure 8-1 or Figure 8-2 for the operation of the PWRTE bit for a particular device. The power-up time delay TPWRT will vary from chip to chip due to VDD, temperature, and process variation. See DC parameters for details. 8.6 Oscillator Start-up Timer (OST) The Oscillator Start-up Timer (OST) provides a 1024 oscillator cycle delay (from OSC1 input) after the PWRT delay ends (Figure 8-10, Figure 8-11, Figure 8-12 and Figure 8-13). This ensures the crystal oscillator or resonator has started and stabilized. The OST time-out (TOST) is invoked only for XT, LP and HS modes and only on Power-on Reset or wake-up from SLEEP. When VDD rises very slowly, it is possible that the TPWRT time-out and TOST time-out will expire before VDD has reached its final value. In this case (Figure 8-13), an external power-on reset circuit may be necessary (Figure 8-9). DS30430C-page 44 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X FIGURE 8-10: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 1 VDD MCLR INTERNAL POR TPWRT PWRT TIME-OUT TOST OST TIME-OUT INTERNAL RESET FIGURE 8-11: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 2 VDD MCLR INTERNAL POR TPWRT PWRT TIME-OUT TOST OST TIME-OUT INTERNAL RESET © 1998 Microchip Technology Inc. DS30430C-page 45 PIC16F8X PIC16F8X FIGURE 8-12: TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO VDD): FAST VDD RISE TIME VDD MCLR INTERNAL POR TPWRT PWRT TIME-OUT TOST OST TIME-OUT INTERNAL RESET FIGURE 8-13: TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO VDD): SLOW VDD RISE TIME V1 VDD MCLR INTERNAL POR TPWRT PWRT TIME-OUT TOST OST TIME-OUT INTERNAL RESET When VDD rises very slowly, it is possible that the TPWRT time-out and TOST time-out will expire before VDD has reached its final value. In this example, the chip will reset properly if, and only if, V1 VDD min. DS30430C-page 46 © 1998 Microchip Technology Inc. PIC16F8X PIC16F8X 8.7 Time-out Sequence and Power-down Status Bits (TO/PD) On power-up (Figure 8-10, Figure 8-11, Figure 8-12 and Figure 8-13) the time-out sequence is as follows: First PWRT time-out is invoked after a POR has expired. Then the OST is activated. The total time-out will vary based on oscillator configuration and PWRTE configuration bit status. For example, in RC mode with the PWRT disabled, there will be no time-out at all. TABLE 8-5 Power-up Reset on Brown-Out A brown-out is a condition where device power (VDD) dips below its minimum value, but not to zero, and then recovers. The device should be reset in the event of a brown-out. To reset a PIC16F8X PIC16F8X device when a brown-out occurs, external brown-out protection circuits may be built, as shown in Figure 8-14 and Figure 8-15. FIGURE 8-14: BROWN-OUT PROTECTION CIRCUIT 1 TIME-OUT IN VARIOUS SITUATIONS Oscillator Configuration 8.8 PWRT Enabled PWRT Disabled Wake-up from SLEEP XT, HS, LP 72 ms + 1024TOSC 1024TOSC 1024TOSC 1024TOSC 1024TOSC 1024TOSC RC 72 ms - VDD - 10k Since the time-outs occur from the POR reset pulse, if MCLR is kept low long enough, the time-outs will expire. Then bringing MCLR high, execution will begin immediately (Figure 8-10). This is useful for testing purposes or to synchronize more than one PIC16F8X PIC16F8X device when operating in parallel. Table 8-6 shows the significance of the TO and PD bits. Table 8-3 lists the reset conditions for some special registers, while Table 8-4 lists the reset conditions for all the registers. TABLE 8-6 TO PD 1 0 x 0 0 1 1 1 x 0 1 0 1 0 VDD 33k STATUS BITS AND THEIR SIGNIFICANCE Condition Power-on Reset Illegal, TO is set on POR Illegal, PD is set on POR WDT Reset (during normal operation) WDT Wake-up MCLR Reset during normal operation MCLR Reset during SLEEP or interrupt wake-up from SLEEP 40k PIC16F8X PIC16F8X This circuit will activate reset when VDD goes below (Vz + 0.7V) where Vz = Zener voltage. FIGURE 8-15: BROWN-OUT PROTECTION CIRCUIT 2 VDD VDD R1 Q1 MCLR R2 40k PIC16F8X PIC16F8X This brown-out circuit is less expensive, although less accurate. Transistor Q1 turns off when VDD is below a certain level such that: VDD · © 1998 Microchip Technology Inc. MCLR R1 R1 + R2 = 0.7V DS30430C-page 47 PIC16F8X PIC16F8X 8.9 Interrupts The PIC16F8X PIC16F8X has 4 sources of interrupt: · · · · External interrupt RB0/INT pin TMR0 overflow interrupt PORTB change interrupts (pins RB7:RB4) Data EEPROM write complete interrupt The interrupt control register (INTCON) records individual interrupt requests in flag bits. It also contains the individual and global interrupt enable bits. The global interrupt enable bit, GIE (INTCON) enables (if set) all un-masked interrupts or disables (if cleared) all interrupts. Individual interrupts can be disabled through their corresponding enable bits in INTCON register. Bit GIE is cleared on reset. The "return from interrupt" instruction, RETFIE, exits interrupt routine as well as sets the GIE bit, which re-enable interrupts. FIGURE 8-16: INTERRUPT LOGIC T0IF T0IE INTF INTE The RB0/INT pin interrupt, the RB port change interrupt and the TMR0 overflow interrupt flags are contained in the INTCON register. When an interrupt is responded to; the GIE bit is cleared to disable any further interrupt, the return address is pushed onto the stack and the PC is loaded with 0004h. For external interrupt events, such as the RB0/INT pin or PORTB change interrupt, the interrupt late