; ------------------------------------------------------------------------ ; FILE : 8digit.asm * ; CONTENTS : Simple low-cost 8-digit counter using a PIC16F84 * ; COPYRIGHT: Peter Halicky OM3CPH * ; AUTHORS : Peter Halicky OM3CPH & Peter Halicky Jr., OM2PH * ; PCB : Tibor Madarasz OM2ATM * ;-------------------------------------------------------------------------- ; E-Mail: peter@halicky.sk ; ; Bratislava, Slovakia, July 2002 - include files modification ; ; To get include files led8t123.exe program should be run. ;-------------------------------------------------------------------------- ; This is 8-digit counter counting up to 16 777 216 Hz. The decimal point ; is after the MHz digit, but can be at any place. More dots can be set. ; ; This project is a variation on later 7-digit frequency meter. ; ; Shematics differs only by 1 transistor connected to pin No. 4 of 4051 ; (it switches anode/cathode of 8ths digit). ; ; PCB is not available....;-( ; ; Power consumption with calculator display: 2.5V/9mA, 3V/13mA, 5V/35mA. ; ; Hardware is very simple: ; ; It contains : PIC 16F84 ; 4051 (BCD -> 1 of 8 decoder) ; 8 NPN low power Si transistors, ; 8-digit calculator display (common cathode), ; some resistors, capacitors and 2 switching diodes ; ; Note: ; "Calculator display" means minimum 8 digit LED multiplexed display. ; Both common cathode and common anode can be used. Software is written ; for common cathode display. For common anode displays it requires very ; slight software and hardware modification. ; ; The counter uses internal prescaler of PIC as low byte of counter, ; TMR0 as middle byte and some register as high byte of counter. ; ; Some ideas were taken from "Simple low-cost digital frequency meter ; using a PIC 16C54" (frqmeter.asm) ; written by James Hutchby, MadLab Ltd. 1996 ; ; ------------------------------------------------------------------------ ; ; This software is free for private usage. It was created for HAM radio ; community members. Commercial exploatation is allowed only with permission ; of authors. ; ; ------------------------------------------------------------------------ IndF equ 00h ; Indirect addr. register Timer0 equ 01h ; TMR0 register - RP0=0 OptionR equ 01h ; Option register - RP0=1 PC equ 02h ; Program counter Status equ 03h ; Status register FSR equ 04h ; Pointer register PortA equ 05h ; Port A - RP0=0 TrisA equ 05h ; Tris A - RP0=1 PortB equ 06h ; Port B - RP0=0 TrisB equ 06h ; Tris B - RP0=1 IntCon equ 0Bh ; 16C84 Index equ 0Ch ; dummy register Count equ 0Dh ; inkremental register Help equ 0Eh ; dummy register LED0 equ 0Fh LED1 equ 010h LED2 equ 011h LED3 equ 012h LED4 equ 013h LED5 equ 014h LED6 equ 015h LED7 equ 016h ; now used for last digit TimerH equ 017h ; higher byte of SW counter LowB equ 018h ; low byte of resulted frequency MidB equ 019h ; middle byte of resulted frequency HigB equ 01Ah ; high byte of resulted frequency Temp equ 01Bh ; temporary register HIndex equ 01Ch ; index register LEDIndex equ 01Dh ; LED pointer ; ------------------------------------------------------------------------ include ; ------------------------------------------------------------------------ ; ; Measuring period is 1 000 000 us. ; Procesor cycle is T = 4/fx us [MHz], fx is Xtal frequency ; ; Number of procesor cycles per measuring period: ; ; N = 1 000 000/T procesor cycles ; N = fx * 1 000 000/4 = 250 000 * fx ; ; The main steps of measuring period: ; ; 1. start measurement, ; 2. precode decimal value of digit to segments, ; 3. if it's 6th digit set decimal point, ; 4. output to PortB, ; 5. output digit number to PortA ; (number positions from left to right are 76543210), ; 6. test TMR0 overflow bite, if YES increase TimerH, ; 7. leave digit to light, ; 8. increase digit number, ; 9. if <8 goto 2, ; 10. else zero digit number, ; decrease counter and goto 2, ; 11. stop measurement, ; 12. shift out precounter content, ; 13. precode 3-byte value into 8 decimal numbers, ; 14. goto 1 ; ; ------------------------------------------------------------------------ ; ; Total timing formula: ; ; N = 250 000 * fx =255*[(36+3*T1+X)*8+2+3*T2+Y]+19+3*T3+Z ; ; where T1,T2,T3 are initial values of timing loops, ; X, Y, Z are additional tunig NOPs. ; let X=0, Y=0 for simplicity ; ------------------------------------------------------------------------ W equ 0 ; destination is accumulator F equ 1 ; register ; ------------------------------------------------------------------------ ; Flag bits: CF equ 0 ; Carry DC equ 1 ; DC ZF equ 2 ; Zero RP0 equ 5 RP1 equ 6 IRP equ 7 ; ------------------------------------------------------------------------ org 0 Start clrf Index clrf LEDIndex clrf LED0 clrf LED1 clrf LED2 clrf LED3 clrf LED4 clrf LED5 clrf LED6 clrf LED7 clrf LowB clrf MidB clrf HigB bsf Status,RP0 movlw b'00010000' ; RA0..RA3 outputs movwf TrisA ; RA4 input movlw b'00000000' ; RB0..RB7 outputs movwf TrisB clrwdt ; movlw b'00100111' ; Prescaler -> Timer0, movwf OptionR ; 1:256, rising edge bcf Status,RP0 ; goto Go ;------------------------------------------------------------------------ ; 3 byte substraction of the constant from the table which sets carry if ; result is negative ;------------------------------------------------------------------------ Subc24 clrf Temp ; it will temporary save CF movf Index,W ; pointer to low byte of constant movwf HIndex ; W -> HIndex call DecTable ; W returned with low byte of constant bsf Status,CF ; set CF subwf LowB,F ; LowB - W -> LowB ; if underflow -> CF=0 btfsc Status,CF goto Step1 bsf Status,CF movlw 1 subwf MidB,F ; decrement MidB ; if underflow -> CF=0 btfsc Status,CF goto Step1 bsf Status,CF movlw 1 subwf HigB,F ; decrement HigB btfsc Status,CF ; if underflow -> CF=0 goto Step1 bsf Temp,CF ; set CF Step1 decf HIndex,F movf HIndex,W ; pointer to middle byte of const call DecTable bsf Status,CF subwf MidB,F ; MidB - W -> MidB btfsc Status,CF ; if underflow -> CF=0 goto Step2 bsf Status,CF movlw 1 subwf HigB,1 ; decrement HigB btfsc Status,CF ; if underflow -> CF=0 goto Step2 bsf Temp,CF ; set CF Step2 decf HIndex,F movf HIndex,W ; pointer to middle byte of constatnt call DecTable bsf Status,CF subwf HigB,F ; HigB - W -> HigB btfsc Status,CF ; if underflow -> CF=0 goto ClearCF bsf Status,CF goto SubEnd ClearCF rrf Temp,CF ; CF -> Status SubEnd retlw 0 ; ------------------------------------------------------------------------ ; 3 byte addition of the constant from the table which sets carry if ; result overflows ; ------------------------------------------------------------------------ Addc24 clrf Temp ; register for temporary storage of CF movf Index,W ; pointer to lower byte of const into W movwf HIndex ; save it into HIndex call DecTable ; W contains low byte of const bcf Status,CF ; clear CF addwf LowB,1 ; W + LowB -> LowB btfss Status,CF ; test overflow goto Add2 bcf Status,CF ; clear CF movlw 1 addwf MidB,F ; increment MidB btfss Status,CF goto Add2 bcf Status,CF movlw 1 addwf HigB,F ; increment HigB btfss Status,CF ; test overflow goto Add2 bsf Temp,CF ; store CF Add2 decf HIndex,F ; pointer to middle byte into W movf HIndex,W call DecTable bcf Status,CF addwf MidB,1 ; W + MidB -> MidB btfss Status,CF goto Add3 bcf Status,CF ; clear CF movlw 1 addwf HigB,1 ; increment HigB btfss Status,CF goto Add3 bsf Temp,CF Add3 decf HIndex,F ; pointer to higher byte into W movf HIndex,W call DecTable bsf Status,CF addwf HigB,F ; W + HigB -> HigB, btfss Status,CF goto ClarCF bsf Status,CF goto AddEnd ClarCF rrf Temp,CF ; CF -> Status AddEnd retlw 0 ; ------------------------------------------------------------------------ ; Tables for 3 byte constants ; ------------------------------------------------------------------------ ; Table of decades ; ------------------------------------------------------------------------ DecTable addwf PC,F ; W + PC -> PC retlw 0 ; 10 retlw 0 ; retlw 0Ah ; retlw 0 ; 100 retlw 0 ; retlw 064h ; retlw 0 ; 1 000 retlw 03h ; retlw 0E8h ; retlw 0 ; 10 000 retlw 027h ; retlw 010h ; retlw 01h ; 100 000 retlw 086h ; retlw 0A0h ; retlw 0Fh ; 1 000 000 retlw 042h ; retlw 040h ; retlw 098h ; 10 000 000 retlw 096h ; retlw 080h ; ; ------------------------------------------------------------------------ ; Table for conversion BCD -> 7 segments ; The view of numbers can be freely modified.... :-) ; ------------------------------------------------------------------------ LEDTable addwf PC,F ; W + PC -> PC retlw b'00111111' ; ..FEDCBA = '0' retlw b'00000110' ; .....CB. = '1' retlw b'01011011' ; .G.ED.BA = '2' retlw b'01001111' ; .G..DCBA = '3' retlw b'01100110' ; .GF..CB. = '4' retlw b'01101101' ; .GF.DC.A = '5' retlw b'01111101' ; .GFEDC.A = '6' retlw b'00000111' ; .....CBA = '7' retlw b'01111111' ; .GFEDCBA = '8' retlw b'01100111' ; .GF..CBA = '9' retlw b'10000000' ; H....... = '.' ; ------------------------------------------------------------------------ ; Routine for conversion of 3 byte number into 8 digits ; ------------------------------------------------------------------------ Go bsf STATUS,RP0 movlw b'00000000' movwf TRISB bcf STATUS,RP0 movlw 7*3-1 ; pointer to dec. table movwf Index ; 7*3-1 -> Index movlw 9 ; maximum of substractions movwf Count ; 9 -> Count clrf Help movlw 7 movwf LEDIndex Divide call Subc24 ; substract untill result is negative, btfsc Status,CF ; if so, add last substracted number goto Add24 ; if not, next digit incf Help,F decf Count,F btfss Status,ZF goto Divide movlw 3 subwf Index,F goto Next Add24 call Addc24 movlw 03h subwf Index,F Next movlw 9 movwf Count movlw LED1 ; LED1 -> W addwf LEDIndex,W ; LED1 + LEDIndex -> W movwf Temp decf Temp,F ; LEDIndex+LED1-1 -> TEMP movf Temp,W movwf FSR ; W -> FSR movf Help,W ; Help -> W clrf Help ; save result at LEDx movwf IndF ; W -> LED(7..1) decf LEDIndex,F movlw 1 addwf Index,W btfss Status,ZF goto Divide movf LowB,W movwf LED0 ; the rest -> LED0 ; ------------------------------------------------------------------------- ; The registers LED0..LED7 are filled with decimal values ; ------------------------------------------------------------------------- clrf TimerH clrf Timer0 nop ; this seems to be suggested nop clrf LEDIndex movlw 0FFh ; set initial counter value movwf Index ; 255 -> Index clrf IntCon ; global INT disable, Timer0 INT disable ; clear Timer0 overflow bite ; ------------------------------------------------------------------------ ; Start measurement: RA3 + RA4 set input ; ------------------------------------------------------------------------ movlw b'00010000' ; all ports set L, RA4 set H movwf PortA bsf Status,RP0 movlw b'00011000' ; RA0..RA2 output,RA3,RA4 input movwf TrisA bcf Status,RP0 ; ------------------------------------------------------------------------- ; 8-step cycle of digits ; ------------------------------------------------------------------------- LEDCycle movlw LED0 addwf LEDIndex,W ; LED1 + LEDIndex -> W movwf FSR ; W -> FSR movf IndF,W ; LED(0..7) -> W call LEDTable ; W contains segments movwf Temp ; test for decimal point movlw 6 ; can be set at any position bsf Status,ZF ; or more than one dot can be set subwf LEDIndex,W ; or none too, of course btfss Status,ZF ; only slight modification of this part goto NoDot ; of source code is needed... bsf Temp,7 ; bcf Temp,7 ; common anode.... NoDot movf Temp,W movwf PortB ; segments -> PortB movf LEDIndex,W ; LEDIndex -> W nop movwf PortA ; digit number -> PortA ; ------------------------------------------------------------------------ ; Test for TMR0 overflow ; ------------------------------------------------------------------------ btfss IntCon,2 goto DoNothing incf TimerH,F ; YES! Increment SW counter bcf IntCon,2 ; clear overflow bite goto O_K DoNothing nop nop nop ; ------------------------------------------------------------------------ ; The first timing loop 2+3*T1+X procesor cycles ; ------------------------------------------------------------------------ O_K movlw T1 movwf Temp Pause decfsz Temp,F goto Pause nop ;+-----------------------------------------------------------------------+ ;| The end of one digit processing | ;+-----------------------------------------------------------------------+ incf LEDIndex,F movlw 8 ; is 8th? bcf Status,ZF subwf LEDIndex,W btfss Status,ZF goto LEDCycle ; next digit nop ; ------------------------------------------------------------------------ ; The second timing loop 2+3*T2+Y procesor cycles ; ------------------------------------------------------------------------ movlw T2 movwf Temp Again decfsz Temp,F goto Again nop ;+-----------------------------------------------------------------------+ ;| The end of one 8-digits processing | ;+-----------------------------------------------------------------------+ clrf LEDIndex decfsz Index,F goto LEDCycle ; next 8xLED nop ; ------------------------------------------------------------------------ ; The third timing loop 2+3*T3+Z procesor cycles ; ------------------------------------------------------------------------ movlw T3 movwf Temp EndPause decfsz Temp,F goto EndPause nop include ; nop ; Z times NOP ; ------------------------------------------------------------------------ ; Final test for TMR0 overflow before stoping measurement ; ------------------------------------------------------------------------ btfss IntCon,2 goto Nothing2Do incf TimerH,F bcf IntCon,2 goto Nx Nothing2Do nop nop nop ; ------------------------------------------------------------------------ ; Stop the measurement ; ------------------------------------------------------------------------ Nx clrw ; For common cathode ;Nx movlw b'11111111' ; For common anode movwf PortB movlw b'00010000' ; RA0..RA3 = 0 movwf PortA ; W -> PortA bsf Status,RP0 movlw b'00010000' ; RA0..RA3 output movwf TrisA ; RA4 input bcf Status,RP0 btfsc IntCon,2 ; really final check incf TimerH,F bcf IntCon,2 ; ------------------------------------------------------------------------ ; Analyse precounter and store counted value in registers ; ------------------------------------------------------------------------ movf Timer0,W movwf MidB ; TMR0 -> MidB movf TimerH,W movwf HigB ; TimerH -> HigB clrf Temp CountIt incf Temp,F bsf PortA,3 ; _| false impulz bcf PortA,3 ; |_ bcf IntCon,2 movf Timer0,W ; actual Timer0 -> W bcf Status,ZF subwf MidB,W btfsc Status,ZF goto CountIt incf Temp,F comf Temp,F incf Temp,F incf Temp,W movwf LowB goto Go ; start new cycle ; ------------------------------------------------------------------------ org 0 end