AN1754 Freescale Semiconductor, Inc. Interfacing MC68HC705J1
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Freescale Semiconductor, Inc.
Interfacing MC68HC705J1A DS1620 Digital Thermometer
Mark Glenewinkel Field Applications Engineering Consumer Systems Group Austin, Texas
Introduction
Measuring temperature always trivial task. Most sensors used read temperature transduce reading electrical signal. These sensors provide voltage level relative temperature reading. This voltage converted digital number using analog-to-digital converter where then processed microprocessor microcontroller. DS1620 Digital Thermometer from Dallas Semiconductor provides single-chip solution that reads temperature converts 9-bit digital value. This data then read from DS1620 serial interface microcontroller (MCU). device also provides three thermal alarm outputs thermostatic control. This application note describes interface between MC68HC705J1A (J1A) DS1620 that used measure temperature range +125 Since does have serial module chip, software driver created provide appropriate serial signals DS1620. Circuitry example
Motorola, Inc., 1998
AN1754
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Freescale Semiconductor, Inc. Application Note
code included here demonstrate interface between parts.
Features
DS1620 provides these features: external components required Supply voltage range volts. Measures temperature from +125 increments. equivalent Fahrenheit range +257 increments. Temperature read 9-bit value. Conversion time second (max). Thermostatic settings user-definable non-volatile (EEPROM). Data transceived 3-wire serial bus. Available 8-pin SOIC packages
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Description
DS1620 provides 9-bit temperature data which indicates temperature chip. data communicated 3-wire serial interface. User-defined temperature settings stored non-volatile memory. Three thermal alarm outputs thermostat, signifying user-defined thresholds. THigh driven high DS1620's temperature greater than equal user-defined temperature, TLow driven high DS1620's temperature less than equal user-defined temperature,
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Application Note DS1620 Hardware Interface
TCOM used derive hysteresis between THigh TLow pins. driven high when temperture exceeds stays high until temperature falls below that
DS1620 Hardware Interface
Freescale Semiconductor, Inc.
Pinout Descriptions
Figure Table illustrate describe DS1620 pinout.
CLK/CONV
THigh TLow TCOM
Figure DS1620 Pinout Table DS1620 Descriptions
Symbol CLK/CONV TCOM TLow THigh Name Data input/output Clock Reset Ground High/low combination trigger temp trigger High temp trigger Supply voltage I/O/PWR Description 3-wire port data 3-wire port clock 3-wire port reset System ground Goes high when temperature exceeds will reset when temperature falls below Goes high when temperature falls below Goes high when temperature exceeds System power range
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Freescale Semiconductor, Inc. Application Note
Block Diagram temperature sensor shown Figure uses oscillators that have particular temperature coefficients derive temperature reading. detailed information this process, consult DS1620 data sheet.
STATUS REGISTER CONTROL LOGIC
TEMPERATURE SENSOR 3-WIRE INTERFACE HIGH TEMPERATURE TRIGGER, TEMPERATURE TRIGGER, DIGITAL COMPARATOR LOGIC
THigh
Freescale Semiconductor, Inc.
TLow
TCOM
Figure DS1620 Block Diagram Serial Timing Read write data transfer timing shown Figure Figure Only logic levels shown here. Consult DS1620 data sheet detailed electrical characteristics needed.
DATA
DATA
FIRST
Figure Serial Data Read Timing
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Application Note DS1620 Hardware Interface
DATA
DATA
FIRST
Figure Serial Data Write Timing
Freescale Semiconductor, Inc.
Thermostat Operation
DS1620 three thermal alarms that trigger output pins THigh, TLow, TCOM. These pins used control closed-loop heating cooling systems activating deactivating system dependent defined temperature boundaries. THigh when temperature exceeds value. Likewise, TLow when temperature falls below value. control oscillation thermostatic system, TCOM used provide hysteresis.
THigh
TLow
TCOM
(°C)
Figure Thermostat Outputs
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Freescale Semiconductor, Inc. Application Note DS1620 Software Interface
Configuration Status Register
configuration status register configures DS1620 different modes operation provide status information device.
DONE 1SHOT
Freescale Semiconductor, Inc.
Figure Configuration Status Register DONE Conversion Complete Flag Temperature conversion complete. Temperature conversion progress. High Temperature Flag temperature greater than equal value register. remains until reset writing this until power removed from device. This allows user determine device ever exceeded limit. temperature less than value register. Temperature Flag temperature less than equal value register. remains until reset writing this until power removed from device. This allows user determine device ever fallen below limit. temperature greater than value register. EEPROM Busy Flag write EEPROM cell progress. This process could take Write EEPROM memory only within temperature range. EEPROM busy.
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Application Note DS1620 Software Interface
operation CLK/CONV acts normal clock. This stored EEPROM cell. CLK/CONV used control conversion start when low. DS1620 shipped with 1SHOT One-Shot Mode DS1620 will execute temperature conversion after start convert command received. This stored EEPROM cell. DS1620 continuously executes temperature conversion process. DS1620 shipped with 1SHOT
Freescale Semiconductor, Inc.
Command
DS1620 command given Table which followed explanation each command. DS1620 commands shown Table since commands receive more accurate temperature reading covered this application note. Table DS1620 Command
Command Read temperature Start convert Stop convert Write Write Read Read Write config Read config Protocol Data After Protocol Read 9-bit data Idle Idle Write 9-bit data Write 9-bit data Read 9-bit data Read 9-bit data Write 8-bit data Read 8-bit data
NOTE:
Writing EEPROM memory cells typically requires room temperature. maximum time specified test code this application note written 50-ms wait period.
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Freescale Semiconductor, Inc. Application Note
Read Temperature Start Convert Reads contents temperature. next nine clocks will transmit 9-bit value serial host.
Begins temperature conversion process. data read witten after this command. continuous mode, part will continually cycle through conversion process. single-shot mode, part will convert temperature reading then remain idle. Stops temperature conversion process. data read written after this command. After command issued, current conversion process finished DS1620 remains idle. Until start convert command issued, DS1620 will remain idle state. Writes high-temperature register (TH). next nine clock cycles will transmit 9-bit value serial DS1620. This sets threshold level operation THigh output pin. Writes low-temperature register (TL). next nine clock cycles will transmit 9-bit value serial DS1620. This sets threshold level operation TLow output pin. Reads value register. next nine clock cycles will transmit 9-bit value serial host. This 9-bit value temperature limit THigh output pin. Reads value register. next nine clock cycles will transmit 9-bit value serial host. This 9-bit value temperature limit TLow output pin. Writes configuration register. next eight clock cycles will transmit 8-bit value serial DS1620. Reads config register. next eight clocks will transmit 8-bit value serial host.
Freescale Semiconductor, Inc.
Stop Convert
Write
Write
Read
Read
Write Config Read Config
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Application Note DS1620 Software Interface
Temperature/Data Relationship
temperature reading provided two's complement 9-bit value. Table illustrates relationship between temperature 9-bit reading. Fahrenheit, table lookup conversion factor must used. Table Temperature/Data Relationship
Temperature +125 Digital Output, $00FA $0032 $0001 $0000 $01FF $01CE $0192 Digital Output, Binary 11111010 00110010 00000001 00000000 11111111 11001110 10010010
Freescale Semiconductor, Inc.
+0.5 -0.5
9-bit temperature value thermostat settings stored 8bit values memory. This illustrated Figure
Address Address
Figure Memory Configuration 9-Bit Data
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Freescale Semiconductor, Inc. Application Note MC68HC705J1A Hardware Interface
With only pins, smaller members HC05 Family. total 1240 bytes erasable programmable read-only memory (EPROM) includes pins. pins used drive DS1620 are: Port This (DQ) used transmit receive data DS1620. Port This (CLK) configured output drive serial clock pin, CLK/CONV, DS1620. Port This (RST) configured output drive reset pin, RST, DS1620.
Freescale Semiconductor, Inc.
schematic used testing J1A-to-DS1620 interface MMEVS development system shown Figure more information HC705J1A, consult MC68HC705J1A Technical Databook, Motorola document order number MC68HC705J1A/D.
DS1620 MMEVS INTERFACE CLK/CONV THigh TLow TCOM
Figure J1A-to-DS1620 Interface Test Circuit
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Application Note MC68HC705J1A Test Software
MC68HC705J1A Test Software
driving manipulation process toggling pins with software instructions create certain hardware peripheral. HC05 provides special instructions specifically manipulate single pins. serial transmission driver been into subroutines called transmitting eight bits data receiving eight bits data. flowcharts DS1620 serial drivers shown Figure through Figure These routines were written especially DS1620 able properly drive other peripherals with serial buses. Figure shows flowchart main test routine. step-bystep sequence testing Write configuration register. This sets DS1620 continuous conversion mode. Write register. value Read register. Store reading locations TH_MSB TH_LSB. Write register. value Read register. Store reading locations TL_MSB TL_LSB. Send start conversion command. Stop code from running emulator allow second time temperature reading. Restart code. temperature read placed locations TEMP_MSB TEMP_LSB. After test sequence finished, temperature values verified. temperature reading again, restart code step
Freescale Semiconductor, Inc.
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Freescale Semiconductor, Inc. Application Note
test thermostat outputs, increase temperature higher than THigh should read Decrease temperature below TLow should read Since DS1620 configured continuous conversion, software needed output thermostatic outputs. This inherent function DS1620. assembly code test routine provided Code Listing.
Development Tools
Freescale Semiconductor, Inc.
interface created tested using these development tools: M68MMPFB0508 Motorola MMEVS platform board M68EM05J1A Motorola emulation module Version 1.02 Editor, assembler, debugger Microcomputer Systems
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Application Note Flowcharts Serial Drivers
Flowcharts Serial Drivers
COUNTER
RIGHT SHIFT ACCA, CARRY
Freescale Semiconductor, Inc.
CARRY
TOGGLE THEN HIGH
DECREMENT
LOOP DONE?
RETURN FROM
Figure Subroutine Flowchart
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Freescale Semiconductor, Inc. Application Note
CONFIGURE INPUT COUNTER
Freescale Semiconductor, Inc.
CARRY
ROTATE RIGHT, CARRY ACCA
DECREMENT
LOOP DONE?
CONFIGURE OUTPUT
RETURN FROM
Figure Subroutine Flowchart
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Application Note Flowcharts Serial Drivers
START
INITIALIZE PORTA DATA DIRECTION PORTA
COMMAND WRITE_CONFIG $00, CONT CONV TOGGLE WAIT MEMORY
Freescale Semiconductor, Inc.
COMMAND WRITE_TH $3C, TOGGLE WAIT MEMORY
COMMAND WRITE_TL $28, TOGGLE WAIT MEMORY
COMMAND READ_TH TH_LSB STORE TH_MSB STORE TOGGLE
COMMAND READ_TL TL_LSB STORE TL_MSB STORE TOGGLE
COMMAND START_CONV TOGGLE
COMMAND READ_TEMP TEMP_LSB STORE TEMP_MSB STORE TOGGLE
INFINITE LOOP
Figure Flowchart Main Test Routine
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Freescale Semiconductor, Inc. Application Note Code Listing
File name: DS1620.ASM Example Code MC68HC705J1A Interface Dallas DS1620 Digital Thermometer Ver: Date: June 1998 Author: Mark Glenewinkel Motorola Field Applications Consumer Systems Group Assembler: 1.02 code explanation flow charts, please consult Motorola Application Note "Interfacing MC68HC705J1A DS1620 Digital Thermometer" Literature AN1754/D SYSTEM DEFINITIONS EQUATES Internal Register Definitions PORTA ;PortA DDRA ;data direction PortA Application Specific Definitions SER_ PORT DQ_DIR READ_TEMP START_CONV STOP_CONV WRITE_TH WRITE_TL READ_TH READ_TL WRITE_CONFIG READ_CONFIG
Freescale Semiconductor, Inc.
;PORTA SER_PORT ;PORTA, clock signal ;PORTA, data signal ;PORTA, reset signal ;PortA Data signal ;instr ;instr ;instr ;instr ;instr ;instr ;instr ;instr ;instr reading temperature starting temperature conv stopping temperature conv writes high temp limit writes temp limit reads high temp limit from reads high temp limit from writes config reads from config
Memory Definitions EPROM $300 RESET $7FE
;start EPROM ;start ;vector reset
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Application Note Code Listing
VARIABLES TEMP_MSB ;temperature reading TEMP_LSB ;temperature reading TH_MSB ;High temp trigger TH_LSB ;High temp trigger TL_MSB ;Low temp trigger TL_LSB ;Low temp trigger MAIN ROUTINE EPROM ;start begining EPROM Intialize Ports START #$07 ;init SER_PORT SER_PORT #$07 ;make SER_PORT pins outputs DDRA Write Config reg, setup #WRITE_CONFIG #$00 bclr RST,SER_PORT bset RST,SER_PORT NV_WAIT #WRITE_TH #$3C #$00 bclr RST,SER_PORT bset RST,SER_PORT NV_WAIT Read verify #READ_TH TH_LSB TH_MSB bclr RST,SER_PORT bset RST,SER_PORT #WRITE_TL #$28 AN1754 MOTOROLA More Information This Product, www.freescale.com cont conv ;load Acca with instruction ;transmit instruction ;load with data ;transmit data ;toggle ;wait memory operation
Freescale Semiconductor, Inc.
;load Acca with instruction ;transmit instruction ;load with data ;transmit data ;load with data ;transmit data ;toggle ;wait memory operation
;load Acca with instruction ;transmit instruction ;receive data ;store away result ;receive data ;store away result ;toggle
;load Acca with instruction ;transmit instruction ;load with data
Freescale Semiconductor, Inc. Application Note
bclr bset #$00 RST,SER_PORT RST,SER_PORT NV_WAIT ;transmit data ;load with data ;transmit data ;toggle ;wait memory operation
Freescale Semiconductor, Inc.
Read verify #READ_TL TL_LSB TL_MSB bclr RST,SER_PORT bset RST,SER_PORT Start temperature conversion #START_CONV bclr RST,SER_PORT bset RST,SER_PORT Read current temperature #READ_TEMP TEMP_LSB TEMP_MSB bclr RST,SER_PORT bset RST,SER_PORT DUMMY DUMMY
;load Acca with instruction ;transmit instruction ;receive data ;store away result ;receive data ;store away result ;toggle
;load Acca with instruction ;transmit instruction ;toggle
;load Acca with instruction ;transmit instruction ;receive data ;store away result ;receive data ;store away result ;toggle
;test sequence over
SUBROUTINES Routine takes contents AccA transmits serially DS1620, first ;set counter WRITE asra bset bclr bclr bset decx ;Carry DQ,SER_PORT CLOCK_IT DQ,SER_PORT CLK,SER_PORT CLK,SER_PORT WRITE ;return from AN1754 More Information This Product, www.freescale.com MOTOROLA ;DQ=1 ;branch clock_it ;DQ=0 ;evens ;CLK=0 ;CLK=1 ;decrement counter
CLOCK_IT
Application Note Code Listing
Routine clocks contents bclr READ bclr brclr rora bset decx bset
DS1620 read data from first AccA DQ_DIR,DDRA ;make input ;set counter CLK,SER_PORT DQ,SER_PORT,J2 CLK,SER_PORT ;CLK=0 ;carry ;put carry into AccA ;CLK=1 ;decrement counter READ DQ_DIR,DDRA ;make output ;return from
Freescale Semiconductor, Inc.
Routine creates routine with 2MHz internal memory correctly NV_WAIT #66T #255T deca decx
VECTOR TABLE RESET START
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Freescale Semiconductor, Inc. Application Note References
MC68HC705J1A Technical Data, document order number MC68HC705J1A/D, Motorola, 1996. M68HC05 Applications Guide, document order number M68HC05AG/AD, Motorola, 1996. DS1620 Data Sheet, Dallas Semiconductor, 1998.
Freescale Semiconductor, Inc.
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