Using MSSP Module Interface Microwire Serial EEPROMs PIC16 Devices

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Using MSSP Module Interface Microwire Serial EEPROMs PIC16 Devices

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AN975
Using MSSP Module Interface Microwire Serial EEPROMs PIC16 Devices
Author: Martin Kvasnicka Microchip Technology Inc. This application note provides assistance source code ease design process interfacing Microchip mid-range PIC16F877A microcontroller Microchip Microwire serial EEPROM. Master Synchronous Serial Port (MSSP) provides simple three-wire connection EEPROM external "glue" logic required. Figure depicts hardware schematic interface between Microchip's Microwire devices Microchip PIC16F877A Microcontroller. schematic shows necessary connections interface microcontroller serial EEPROM (software written assuming these connections).
There many different microcontrollers market today that being used embedded control applications. Many these embedded control systems need nonvolatile memory. Because their small footprint, byte level flexibility, requirement, power consumption cost, serial EEPROMs popular choice nonvolatile storage. Microchip Technology addressed these needs offering full line serial EEPROMs covering industry standard serial communication protocol two-wire (I2CTM), three-wire (Microwire), SPIcommunication. Serial EEPROM devices available variety densities, operational voltage ranges, packaging options.
FIGURE
CIRCUIT PIC16F877A SERIES (MICROWIRE) DEVICE
MCLR/VPP RA0/AN0 RA1/AN1 RA2/AN2VREFRA3/AN3/VREF+ RA4/T0CKI/C1OUT RA5/AN4/SSC2OUT RE0/RD/AN5 RE1/WR/AN6 RE2/CS/AN7 OSC1/CLK1 OSC2/CLK0 RC0/T10S0T1CKI RC1/T10SI/CCP2 RC2/CCP1 RC3/SCK/SCL RD0/PSP0 RD1/PSP1 RB7/PGD RB6/PGC RB3/PGM RB0/INT RD7/PSP7 RD6/PSP6 RD5/PSP5 RD4/PSP4 RC7/RX/DT RC6TX/CK RC5/SDO RC4/SDI/SDA RD3/PSP3 RD2PSP2
PDIP (600 MIL)
93XXXXX
PIC16F877A
should always have pull-down resistor protect against data corruption during power-up power-down Microcontroller. available only 93XX76X 93XX86X devices. Pull-up resistor suggested ~10K ohm.
2005 Microchip Technology Inc.
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THEORY OPERATION
port communicate with Microchip's Microwire Serial EEPROMs, bytes output 93XXXX must aligned such that address (LSB) byte output. From there bits should fill byte from right left consecutively. more that bits required, then bytes will required output. This same method will work 93XXXX series device. Since more than bits necessary control 93LC66C, consecutive bytes required. High Byte (Start bit, opcode bits address MSb)
FIRMWARE DESCRIPTION
purpose program show individual features Microwire protocol give code samples Start bit, opcodes addressing schemes that basic building blocks program shown. waveforms provided will shown from active disable entire instruction seen. ease interpretation serial data, data sheet waveform will provided below oscilloscope screen shot.
High Byte configured following format: Start bit. opcode opcode LSb. address that required address bytes. line before byte output, because leading output 93XXXX prevents Start from being recognized 93XXXX until first high sent. Byte Address bits)
Byte contains A7-A0, which remaining address bits required access bytes. Data output from master MUST falling edge clock that read from 93XXXX next rising edge. Receiving data from 93XXXX MUST also happen falling edge clock because data output from 93XXXX rising edge clock. This requires clock phase (bit SSPCON register) MSSP port opposite receiving than transmitting. clock phase needs cleared transmitting receiving data.
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2005 Microchip Technology Inc.
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WRITE ENABLE
Figure shows example Erase/Write Enable (EWEN) command. Chip Select brought high (active), Start opcode sent through MSSP port. EWEN command must given before write attempted. device will enabled writes until Erase/Write Disable command given device powered down.
FIGURE
ERASE/WRITE ENABLE (EWEN)
TCSL
2005 Microchip Technology Inc.
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WRITE COMMAND (START BIT, OPCODE, ADDRESS DATA)
Figure shows example Write command. device selected high byte sent which contains Start bit, opcode address. second byte sent which contains rest address bits A7-A0. Finally, data clocked this case 0x5A. When Chip Select toggled, internal write cycle initiated. Once internal write cycle begun Ready/ Busy signal polled check when write finishes. delay needs added Ready/Busy status being polled. This code uses Ready/Busy polling.
FIGURE
WRITE COMMAND, ADDRESS DATA
TCSL
Ready
High-Z
Busy
High-Z
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2005 Microchip Technology Inc.
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READY/BUSY POLLING
After valid Write command given, line 93XXXX monitored check internal write cycle been initiated continuously monitored look write cycle. oscilloscope plot below shows that device selected line approximately before device brings line high, indicating that write cycle complete.
FIGURE
READY/BUSY POLLING
2005 Microchip Technology Inc.
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AN975
READ COMMAND (START BIT, OPCODE, ADDRESS DATA)
Figure shows example Read command. device selected high byte sent which contains Start bit, opcode address. second byte sent which contains rest address bits A7-A0 (0x10). this point device gets ready send data out. controller needs send dummy byte order clock signals sent data read device into microcontroller. this case, data being read 0x5A.
FIGURE
READ COMMAND
High-Z
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2005 Microchip Technology Inc.
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ERASE/WRITE DISABLE COMMAND
Once device write finished, Write Disable (EWDS) command should given (see Figure This command consists Start four-bit opcode (0000). Except first high order address bits A7), address bits (set zeros this example) "don't cares." Address bits used define third fourth opcode bits. EWDS command should always sent device after completing write prior powering down device/system.
FIGURE
ERASE/WRITE DISABLE COMMAND
TCSL
2005 Microchip Technology Inc.
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CONCLUSION
These some basic features Microwire communications using MSSP module Microchip's mid-range devices. code highly portable used many devices that have MSSP module with very minor modifications. Using code provided, designers begin build their Microwire libraries simple complex needed. code tested Microchip's PICDEM2 Plus Demonstration Board with connections shown Figure
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2005 Microchip Technology Inc.
Note following details code protection feature Microchip devices: Microchip products meet specification contained their particular Microchip Data Sheet. Microchip believes that family products most secure families kind market today, when used intended manner under normal conditions. There dishonest possibly illegal methods used breach code protection feature. these methods, knowledge, require using Microchip products manner outside operating specifications contained Microchip's Data Sheets. Most likely, person doing engaged theft intellectual property. Microchip willing work with customer concerned about integrity their code. Neither Microchip other semiconductor manufacturer guarantee security their code. Code protection does mean that guaranteeing product "unbreakable."
Code protection constantly evolving. Microchip committed continuously improving code protection features products. Attempts break Microchip's code protection feature violation Digital Millennium Copyright Act. such acts allow unauthorized access your software other copyrighted work, have right relief under that Act.
Information contained this publication regarding device applications like provided only your convenience superseded updates. your responsibility ensure that your application meets with your specifications. MICROCHIP MAKES REPRESENTATIONS WARRANTIES KIND WHETHER EXPRESS IMPLIED, WRITTEN ORAL, STATUTORY OTHERWISE, RELATED INFORMATION, INCLUDING LIMITED CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY FITNESS PURPOSE. Microchip disclaims liability arising from this information use. Microchip's products critical components life support systems authorized except with express written approval Microchip. licenses conveyed, implicitly otherwise, under Microchip intellectual property rights.
Trademarks Microchip name logo, Microchip logo, Accuron, dsPIC, KEELOQ, microID, MPLAB, PIC, PICmicro, PICSTART, MATE, PowerSmart, rfPIC, SmartShunt registered trademarks Microchip Technology Incorporated U.S.A. other countries. AmpLab, FilterLab, Migratable Memory, MXDEV, MXLAB, PICMASTER, SEEVAL, SmartSensor Embedded Control Solutions Company registered trademarks Microchip Technology Incorporated U.S.A. Analog-for-the-Digital Age, Application Maestro, dsPICDEM, dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR, FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming, ICSP, ICEPIC, MPASM, MPLIB, MPLINK, MPSIM, PICkit, PICDEM, PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo, PowerMate, PowerTool, rfLAB, rfPICDEM, Select Mode, Smart Serial, SmartTel, Total Endurance WiperLock trademarks Microchip Technology Incorporated U.S.A. other countries. SQTP service mark Microchip Technology Incorporated U.S.A. other trademarks mentioned herein property their respective companies. 2005, Microchip Technology Incorporated, Printed U.S.A., Rights Reserved. Printed recycled paper.
Microchip received ISO/TS-16949:2002 quality system certification worldwide headquarters, design wafer fabrication facilities Chandler Tempe, Arizona Mountain View, California October 2003. Company's quality system processes procedures PICmicro® 8-bit MCUs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory analog products. addition, Microchip's quality system design manufacture development systems 9001:2000 certified.
2005 Microchip Technology Inc.
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03/01/05
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2005 Microchip Technology Inc.

Using MSSP Module Interface Microwire Serial EEPROMs PIC16 Devices

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