;******************************************************************* ; FMETER.ASM ; 4 digit 0-9999 kHz frequency-meter ; made by Dr. Dmitry Albov, Laboratory of Structural Chemistry, ; Moscow State University ; e-mail: dmitryalbov@mail.ru ; ;******************************************************************* ; processor 16f84a ;for Microchip MPLAB #include p16f84a.inc LIST p=16F84A __config _HS_OSC & _WDT_OFF & _PWRTE_ON ; ;status registers: pc equ 02 ;program counter porta equ 05 ;I/O register portb equ 06 ;I/O register status equ 03 ;status register tmr equ 01 ;8-bit counter trisa equ 0x5 ;port "a" direction register trisb equ 0x6 ;port "b" direction register intcon equ 0x0B ;interrupt control register ; ;general registers: H_byte equ 0x10 ;high byte of measured frequency L_byte equ 0x11 ;low byte of measured frequency count_r equ 0x12 ;refresh counter U equ 0x13 ;units D equ 0x14 ;tens H equ 0x15 ;hundreds M equ 0x16 ;thousands count1 equ 0x17 ;counter register N equ 0x18 ;general register ; ;*************************** MAIN PROGRAM org 0 start movlw 0x27 option ;load 00100111 in option register movlw 0x10 movwf intcon clrf porta clrf portb bsf status,5 movlw 0x10 movwf trisa ;porta:0-3 = output, porta:4 = input clrf trisb ;potrb:0-7 = output bcf status,5 movlw 0x08 ;all the segments are switched on movwf U ;to test the displays movwf D movwf H movwf M movlw .125 ;test refresh 0.5 sec movwf count_r loop1 call refresh ;refresh of the displays decfsz count_r goto loop1 work clrf tmr ;clear timer clrwdt ;clear prescaler bsf status,5 movlw b'10000000' ; portB:7 - input, enable count movwf trisb ;- bcf status,5 ; | movlw .99 ; | movwf count1 ; | ms1 nop ; | nop ; | nop ; | nop ; | nop ; | nop ; |- This is 1 millisecond measuring time for 4.000 MHz crystal. nop ; |- DO NOT CHANGE THIS BLOCK until you need calibration! decfsz count1 ; | goto ms1 ; | nop ; | nop ; | nop ; | nop ; |If you need calibration, add or remove one or more NOPs here. nop ; | nop ; | bsf status,5 ; | clrf trisb ;- PortB - output, disable count bcf status,5 call prescaler ;put the counted number into H_byte:L_byte call refresh ;We need to refresh the display between measuring period and long calculations to reduce blinking clrf M ;clear display registers clrf H clrf D clrf U call bin2bcd ;convert binary H_byte:L_byte to binary coded decimal M:H:D:U, 4 digits call adjust ;decimal adjust after conversion movlw .125 movwf count_r loopr call refresh ;call refresh 125 times - it is about 0.5 sec decfsz count_r goto loopr goto work ;work FOREVER! (or until power off...) ; ; ***************************** Delay subroutine delay movlw .100 ; - movwf count1 ; | d1 nop ; | nop ; | nop ; | nop ; |-about 1 millisecond delay, we do not need exact time here nop ; | nop ; | nop ; | decfsz count1 ; | goto d1 ; | return ; - ; ********************************************* BCD -> 7-segment table translation segments addwf pc ; 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'01101111' ; .GF.DCBA = '9' ; ***************************** display refresh subroutine: 250 mSec refresh movfw M ;display thousands call segments movwf portb bsf porta,0 call delay bcf porta,0 movfw H ;display hundreds call segments movwf portb bsf porta,1 call delay bcf porta,1 movfw D ;display tens call segments movwf portb bsf porta,2 call delay bcf porta,2 movfw U ;display units call segments movwf portb bsf porta,3 call delay bcf porta,3 return ; ************** subroutine to extract the value contained in prescaler. Frequency=H_byte:L_byte=tmr:prescaler prescaler movfw tmr movwf H_byte ;save the counter into H_byte clrf N p1 bcf portb,7 bsf portb,7 bcf portb,7 ;give an edge to the input controller incf N movfw H_byte ;make a copy of H_byte into W xorwf tmr,0 ;check if tmr has been changed btfsc status,2 goto p1 ;if NOT, repeat movlw 0xFF movwf L_byte movfw N ; N = how many pulses were needed to complete prescaler to 256 subwf L_byte ;-|__ L_byte=256-N incf L_byte ;-| return ; ****************************** BIN -> BCD conversion H_byte:L_byte -> M:H:D:U bin2bcd btfss H_byte,5 ;check bit5 of H_byte goto b1 movlw 0x08 addwf M movlw 0x01 addwf H movlw 0x09 addwf D movlw 0x02 addwf U ;if bit5=1 then add 8192 b1 btfss H_byte,4 ;check bit4 of H_byte goto b2 movlw 0x04 addwf M movlw 0x09 addwf D movlw 0x06 addwf U ;if bit4=1 then add 4096 b2 btfss H_byte,3 ;check bit3 of H_byte goto b3 movlw 0x02 addwf M movlw 0x04 addwf D movlw 0x08 addwf U ;if bit3=1 then add 2048 b3 btfss H_byte,2 ;check bit2 of H_byte goto b4 movlw 0x01 addwf M movlw 0x02 addwf D movlw 0x04 addwf U ;if bit2=1 then add 1024 b4 btfss H_byte,1 ;check bit1 of H_byte goto b5 movlw 0x05 addwf H movlw 0x01 addwf D movlw 0x02 addwf U ;if bit1=1 then add 512 b5 btfss H_byte,0 ;check bit0 of H_byte goto b6 movlw 0x02 addwf H movlw 0x05 addwf D movlw 0x06 addwf U ;if bit0=1 then add 256 b6 btfss L_byte,7 ;check bit7 of L_byte goto b7 movlw 0x01 addwf H movlw 0x02 addwf D movlw 0x08 addwf U ;if bit7=1 then add 128 b7 btfss L_byte,6 ;check bit6 of L_byte goto b8 movlw 0x06 addwf D movlw 0x04 addwf U ;if bit6=1 then add 64 b8 btfss L_byte,5 ;check bit5 of L_byte goto b9 movlw 0x03 addwf D movlw 0x02 addwf U ;if bit5=1 then add 32 b9 btfss L_byte,4 ;check bit4 of L_byte goto b10 movlw 0x01 addwf D movlw 0x06 addwf U ;if bit4=1 then add 16 b10 btfss L_byte,3 ;check bit3 of L_byte goto b11 movlw 0x08 addwf U ;if bit3=1 then add 8 b11 btfss L_byte,2 ;check bit2 of L_byte goto b12 movlw 0x04 addwf U ;if bit2=1 then add 4 b12 btfss L_byte,1 ;check bit1 of L_byte goto b13 movlw 0x02 addwf U ;if bit1=1 then add 2 b13 btfss L_byte,0 ;check bit0 of L_byte goto b14 movlw 0x01 addwf U ;if bit0=1 then add 1 b14 return ; ****************************** BCD ajust after conversion adjust movfw U movwf N ;make a copy of U in N movlw 0x0A subwf N,1 ;test if U<10 btfss status,0 goto a1 ;if U<10 then adjust is not needed, go to next digit movlw 0x0A ;if U>10 then U=U-10 and D=D+1 subwf U,1 incf D,1 goto adjust ;repeat a1 movfw D movwf N ;make a copy of D in N movlw 0x0A subwf N,1 ;test if D<10 btfss status,0 goto a2 ;if D<10 then adjust is not needed, go to next digit subwf D,1 ;if D>10 then D=D-10 and H=H+1 incf H,1 goto a1 ;repeat a2 movfw H movwf N ;make a copy of H in N movlw 0x0A subwf N,1 ;test if H<10 btfss status,0 goto a3 ;if H<10 then adjust is not needed, go to next digit subwf H,1 ;if H>10 then H=H-10 and M=M+1 incf M,1 goto a2 ;repeat a3 return END ;----------------