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Assembly Source File | 1989-07-11 | 12.4 KB | 364 lines

* Micro Cornucopia Magazine Issue #49 * 6805 Controller Example Project Code * * EXAMPLE.ASM * * Sample program showing design of control program, to be run from * the EPROM of an MC68HC705 MCU. The program monitors one channel * of A/D, using an MC145041 Serial A/D converter chip. LEDs are * sequenced as needed, depending on the value of the A/D channel. * * The A/D chip connects to the MCU through the Serial Peripheral * Interface (SPI). The chip select line for the A/D is bit 3 of MCU * Port C; a low on this line selects the A/D chip. * * Three status LEDs connect to bits 0-2 of MCU port C. LED1 (port C, * bit 0) stays on at all times, to show the program is actually running. * LED2 (port C, bit 1) stays on at all times, provided the A/D value * stays below $40. If the value rises to between $40 and $7F, LED2 * blinks once per second. If the value rises above $7F, LED2 goes out. * LED3 (port C, bit 2) only comes on if the A/D value reaches $80. * If the value lies between $80 and $BF, LED3 stays on. If the value * rises above $BF, LED3 blinks once per second. * * The code for routine TIME and much of the code in MAIN comes directly * from the example development project in the M68HC05 Microcontroller * Applications Guide. Refer to pages 4-24 for the original listing. * The same program is provided by Motorola as Freeware and as source * code on the program disc that accompanies the Applications Guide. * I would give credit to the original programmer, if I knew who he/she * was. * * * Register equates * PORTA EQU $00 Port A data register PORTB EQU $01 Port B data register PORTC EQU $02 Port C data register PORTD EQU $03 Port D data register DDRA EQU $04 Data direction, Port A DDRB EQU $05 Data direction, Port B DDRC EQU $06 Data direction, Port C SPCR EQU $0A SPIE,SPE,-,MSTR;CPOL,CPHA,SPR1,SPR0 SPSR EQU $0B SPIF,WCOL,-,MODF;-,-,-,- SPDR EQU $0C SPI Data BAUD EQU $0D -,-,SCP1,SCP0;-,SCR2,SCR1,SCR0 SCCR1 EQU $0E R8,T8,-,M;WAKE,-,-,- SCCR2 EQU $0F TIE,TCIE,RIE,ILIE;TE,RE,RWU,SBK SCSR EQU $10 TDRE,TC,RDRF,IDLE;OR,NF,FE,- SCDR EQU $11 SCI Data RDR EQU $11 SCI Receive Data (same as SCDR) TDR EQU $11 SCI Transmit Data (same as SCDR) TCR EQU $12 ICIE,OCIE,TOIE,0;0,0,IEGE,OLVL TSR EQU $13 ICF,OCF,TOF,0; 0,0,0,0 ICAP EQU $14 Input Capture Reg (Hi-$14, Lo-$15) OCMP EQU $16 Output Compare Reg (Hi-$16, Lo-$17) TCNT EQU $18 Timer Count Reg (Hi-$18, Lo-$19) ALTCNT EQU $1A Alternate Count Reg (Hi-$1A, Lo-$1B) * * Following equates are timer values to produce a 50 msec delay * using the MCU timing registers. Use ONLY one pair of values, * depending on the MCU timing crystal for the target system. * TMRCNTL EQU $D4 FOR 2.0 MHZ CLOCK TMRCNTH EQU $30 * TMRCNTL EQU $6A FOR 1.0 MHZ CLOCK * TMRCNTH EQU $18 ORG $50 START OF VARIABLES IN RAM TEMPA RMB 1 TEMP STORAGE FOR ACC TEMPX RMB 1 TEMP STORAGE FOR XR TIC RMB 1 50 MSEC TICS; 0-19, 20 TICS = 1 SEC SEC RMB 1 CURRENT TIME IN SECONDS MIN RMB 1 CURRENT TIME IN MINUTES HR RMB 1 CURRENT TIME IN HOURS AMPM RMB 1 CURRENT TIME (0 = AM, 1 = PM) DAY RMB 1 CURRENT DAY (1 = SUN...7 = SAT) LED1 RMB 1 CONTROL BYTE FOR LED1 (0 = DARK) LED2 RMB 1 CONTROL BYTE FOR LED2 (0 = DARK) LED3 RMB 1 CONTROL BYTE FOR LED3 (0 = DARK) ORG $0100 START OF PROGRAM IN ROM INIT RSP INITIALIZE THE STACK POINTER * * Set timer and SPI characteristics. * LDA #$50 SPI: MCU IS MASTER, 2 USEC CLOCK STA SPCR WRITE TO SPI CONTROL REG CLRA TIMER: NO INTERRUPTS OR PINS USED STA TCR WRITE TO TIMER CONTROL REG * * Set up port C, bits 0-2 for output as LED controllers. * Clear LED control bytes (turns LEDs off later). * * Set up port C, bit 3 for output as A/D chip select. * LDA #$0F BITS 0-3 = OUTPUT, ALL OTHERS = INPUT STA DDRC SETUP PORT C CLR LED1 SHOW ALL LEDS AS OFF CLR LED2 CLR LED3 * * Initialize clock to show 12:00 AM Sunday. * CLR TIC ZERO THE TIC COUNTER CLR SEC SET SECONDS TO 0 LDA #12 SET HOUR TO NOON STA HR CLR MIN SET MINUTES TO 0 CLR AMPM SET TO MORNING LDA #1 SET DAY TO SUNDAY STA DAY * * ----- END OF INITIALIZATION ----- * * * MAIN * * This loop gets executed once each 50 msec, based on the * MCU's internal timer. The compare register is loaded * with a target value. When the timer hits that value, * bit 6 of the Output Compare Register (OCR) gets set, * marking the end of a 50 msec interval. * * At each interval, the timer is reloaded, the time/day clock * is updated, and the chain of subroutines at the bottom of * the loop is executed. So long as the chain takes no more * than 50 msec to complete, the MCU will stay on-time. * MAIN EQU * BRCLR 6,TSR,MAIN LOOP HERE UNTIL TIME OUT LDA OCMP+1 LOW BYTE OF OCR ADD #TMRCNTL CALCULATE NEW TIMER TARGET STA TEMPA LDA OCMP DO BOTH HALVES OF 16-BIT VALUE ADC #TMRCNTH STA OCMP LDA TEMPA STA OCMP+1 TIMER TARGET RELOADED LDA TIC GET TIC COUNTER INCA BUMP IT STA TIC AND SAVE NEW VALUE CMP #20 DONE ONE SECOND YET? BLO ARNC1 IF NOT, DON'T CLEAR TIC CLR TIC YES, START A NEW SECOND ARNC1 EQU * * * End of the timing loop; following chain of subroutine calls * must complete within 50 msecs. * JSR TIME UPDATE TIME-OF-DAY CLOCK JSR PROCESS READ A/D, SET LED CONTROL BYTES JSR LEDS PROCESS PENDING LED COMMANDS BRA MAIN DO IT ALL AGAIN * * TIME * * Update the time-of-day clock. * TIME EQU * TST TIC Check for TIC=zero BNE XTIME If not; just exit INC SEC SEC=SEC+1 LDA #60 CMP SEC Did SEC -> 60 ? BNE XTIME If not; just exit CLR SEC Seconds rollover INC MIN MIN=MIN+1 CMP MIN A still 60; MIN=60 ? BNE XTIME If not; just exit CLR MIN Minutes rollover INC HR HR=HR+1 LDA HR For comparisons CMP #13 HR=13 ? BNE ARNS1 If not; skip LDA #1 STA HR Set HR=1 BRA XTIME Exit ARNS1 CMP #12 HR=12 ? BNE XTIME If not; just exit LDA AMPM EOR #%00000001 Invert AM/PM bit STA AMPM 0=AM, 1=PM BNE XTIME If not AM now; just exit INC DAY DAY=DAY+1 LDA DAY CMP #8 Day rollover ? BNE XTIME If not; just exit LDA #1 STA DAY Set Day to 1 (SUN) XTIME RTS * * LEDS -- Process any pending LED commands, based on the LED * control bytes. * * Each LED control byte determines whether an LED is turned on * or off. If the byte is 0, that LED is always turned off by this * routine. If the byte is not 0, the corresponding LED is always * turned on and the control byte is decremented. * * If this routine is called each slice (20 times per second), the * longest period of time an LED can remain lit without intervention * is 255 * 50 msec = 12750 msec or 12.75 seconds. * LEDS TST LED1 NEED TO TURN ON LED1? BEQ LED1N BRANCH IF TIME TO TURN OFF BCLR 0,PORTC TURN ON LED1 (ACTIVE LOW) DEC LED1 COUNT THIS 50 MSEC BRA LED2T GO TEST LED2 LED1N BSET 0,PORTC TURN OFF LED1 LED2T TST LED2 DO IT AGAIN FOR LED2 BEQ LED2N BCLR 1,PORTC USE BIT 1 FOR LED2 DEC LED2 BRA LED3T LED2N BSET 1,PORTC LED3T TST LED3 SAME AGAIN FOR LED3 BEQ LED3N BCLR 2,PORTC USE BIT 2 FOR LED3 DEC LED3 BRA LEDSX LED3N BSET 2,PORTC LEDSX RTS * * PROCESS -- Change LED control bytes as needed to reflect current * status of A/D input. * * If TIC holds a 0 (first 50 msec slice of each second), read channel * 0 of the A/D and trash the returned value. * * If TIC holds a 1 (second 50 msec slice of each second), read * channel 0 of the A/D and process the LED states, depending on the * following: * * Value range Action taken * ----------- -------------------------------------------- * * $00 - $3F Turn LED2 on for one second, turn LED3 off. * $40 - $7F Turn LED2 on for .5 seconds, turn LED3 off. * $80 - $BF Turn LED2 off, turn LED3 on for one second. * $C0 - $FF Turn LED2 off, turn LED3 on for .5 seconds. * * All other values of TIC are ignored by this routine. Note * that LED1 is always on. * PROCESS LDA #$FF GET LONGEST ON-TIME STA LED1 ALWAYS LEAVE LED1 ON LDA TIC GET CURRENT TIC VALUE BNE PROCS1 BRANCH IF NOT FIRST TIC BSR A2D LOAD UP CHANNEL 0 VALUE BRA PROCSX AND LEAVE PROCS1 CMP #1 IS THIS THE SECOND TIC? BNE PROCSX BRANCH IF NOT CLRA LOAD UP CHANNEL 0 AGAIN BSR A2D AND READ THAT CHANNEL CMP #$40 IS VALUE IN GOOD RANGE? BHS PROCS2 BRANCH IF NOT CLR LED3 TURN OFF LED3 LDA #20 TURN ON LED2 FOR 1 SECOND STA LED2 BRA PROCSX AND LEAVE PROCS2 CMP #$80 IS VALUE IN FAIR RANGE? BHS PROCS3 BRANCH IF NOT CLR LED3 TURN OFF LED3 LDA #10 TURN ON LED2 FOR .5 SECONDS STA LED2 BRA PROCSX AND LEAVE PROCS3 CMP #$C0 IS VALUE IN POOR RANGE? BHS PROCS4 BRANCH IF NOT CLR LED2 TURN OFF LED2 LDA #20 TURN ON LED3 FOR 1 SECOND STA LED3 BRA PROCSX AND LEAVE PROCS4 CLR LED2 MUST BE BAD, SHUT OFF LED2 LDA #10 TURN ON LED3 FOR .5 SECONDS STA LED3 PROCSX RTS * * A2D -- Read selected channel of serial A/D (MC145041). * * Enter with A/D channel number in ACC. Returns analog value * in ACC. Assumes chip select line to A/D chip is driven by * port C, bit 3 (active low). * * Note that the value returned by A2D corresponds to the most * recent previous channel number transmitted, not the current * channel number! Therefore, unless you know for a fact that * the last channel number you sent was the one you want to read * now, you had better call this routine twice, using the same * channel number. * A2D TST SPSR CLEAR SPIF BCLR 3,PORTC PULL CHIP SELECT LINE LOW ASLA MOVE CHANNEL NUMBER TO HIGH NYBBLE ASLA ASLA ASLA STA SPDR SEND CHANNEL TO SPI SPIFLP BRCLR 7,SPSR,SPIFLP WAIT UNTIL COMPLETE BSET 3,PORTC RELEASE CHIP SELECT LDA SPDR GET VALUE RETURNED RTS * * Set up the RESET vector. This is required for code that will * be moved into the MCU's EPROM for later execution. * ORG $1FFE RESET VECTOR FDB INIT POINT TO START OF PROGRAM