;************************************************************************ ; * ; Filename: L8-Count_7seg_BCD.asm * ; Date: 19/11/09 * ; File Version: 1.1 * ; * ; Author: David Meiklejohn * ; Company: Gooligum Electronics * ; * ;************************************************************************ ; * ; Architecture: Baseline PIC * ; Processor: 16F505 * ; * ;************************************************************************ ; * ; Files required: none * ; * ;************************************************************************ ; * ; Description: Lesson 8, example 3 * ; * ; Demonstrates BCD storage and counting * ; * ; 3 digit 7-segment LED display: 1 digit minutes, 2 digit seconds * ; counts in seconds 0:00 to 9:59 then repeats, * ; with timing derived from int 4 MHz oscillator * ; (seconds count stored in BCD format) * ; * ;************************************************************************ ; * ; Pin assignments: * ; RB2, RC0-5 - 7-segment display bus (common cathode) * ; RB4 - minutes enable (active high) * ; RB1 - tens enable * ; RB0 - ones enable * ; * ;************************************************************************ list p=16F505 #include radix dec ;***** CONFIGURATION ; ext reset, no code protect, no watchdog, 4MHz int clock __CONFIG _MCLRE_ON & _CP_OFF & _WDT_OFF & _IntRC_OSC_RB4EN ; pin assignments #define MINUTES PORTB,4 ; minutes enable #define TENS PORTB,1 ; tens enable #define ONES PORTB,0 ; ones enable ;***** VARIABLE DEFINITIONS UDATA_SHR digit res 1 ; digit to be displayed UDATA mpx_cnt res 1 ; multiplex counter mins res 1 ; time count: minutes secs res 1 ; seconds (BCD) ;***** RESET VECTOR ***************************************************** RESET CODE 0x000 ; effective reset vector movwf OSCCAL ; update OSCCAL with factory cal value pagesel start goto start ; jump to main program ;***** Subroutine vectors set7seg ; display digit on 7-segment display pagesel set7seg_R goto set7seg_R ;***** MAIN PROGRAM ***************************************************** MAIN CODE ;***** Initialisation start clrw ; configure PORTB and PORTC as all outputs tris PORTB tris PORTC movlw b'11010111' ; configure Timer0: ; --0----- timer mode (T0CS = 0) -> RC5 usable ; ----0--- prescaler assigned to Timer0 (PSA = 0) ; -----111 prescale = 256 (PS = 111) option ; -> increment every 256 us ; (TMR0<2> cycles every 2.048ms) banksel mins ; start with count = 0 clrf mins clrf secs ;***** Main loop main_loop ; multiplex display for 1 sec movlw 1000000/2048/3 ; display each of 3 digits for 2.048 ms each movwf mpx_cnt ; repeat multiplex loop for approx 1 second mplex_loop ; display minutes for 2.048 ms w60_hi btfss TMR0,2 ; wait for TMR0<2> to go high goto w60_hi movf mins,w ; get minutes digit pagesel set7seg call set7seg ; then output it pagesel $ bsf MINUTES ; enable minutes display w60_lo btfsc TMR0,2 ; wait for TMR<2> to go low goto w60_lo ; display tens for 2.048 ms w10_hi btfss TMR0,2 ; wait for TMR0<2> to go high goto w10_hi swapf secs,w ; get tens digit andlw 0x0F ; from high nybble of seconds pagesel set7seg call set7seg ; then output it pagesel $ bsf TENS ; enable tens display w10_lo btfsc TMR0,2 ; wait for TMR<2> to go low goto w10_lo ; display ones for 2.048 ms w1_hi btfss TMR0,2 ; wait for TMR0<2> to go high goto w1_hi movf secs,w ; get ones digit andlw 0x0F ; from low nybble of seconds pagesel set7seg call set7seg ; then output it pagesel $ bsf ONES ; enable ones display w1_lo btfsc TMR0,2 ; wait for TMR<2> to go low goto w1_lo decfsz mpx_cnt,f ; continue to multiplex display goto mplex_loop ; until 1 sec has elapsed ; increment counters incf secs,f ; increment seconds movf secs,w ; if ones overflow, andlw 0x0F xorlw .10 btfss STATUS,Z goto end_inc movlw .6 ; BCD adjust seconds addwf secs,f movlw 0x60 xorwf secs,w ; if seconds = 60, btfss STATUS,Z goto end_inc clrf secs ; reset seconds to 0 incf mins,f ; and increment minutes movlw .10 xorwf mins,w ; if minutes overflow, btfsc STATUS,Z clrf mins ; reset minutes to 0 end_inc goto main_loop ; repeat forever ;***** LOOKUP TABLES **************************************************** TABLES CODE 0x200 ; locate at beginning of a page ; Lookup pattern for 7 segment display on port B get7sB addwf PCL,f retlw b'000000' ; 0 retlw b'000000' ; 1 retlw b'000100' ; 2 retlw b'000100' ; 3 retlw b'000100' ; 4 retlw b'000100' ; 5 retlw b'000100' ; 6 retlw b'000000' ; 7 retlw b'000100' ; 8 retlw b'000100' ; 9 ; Lookup pattern for 7 segment display on port C get7sC addwf PCL,f retlw b'111111' ; 0 retlw b'011000' ; 1 retlw b'110110' ; 2 retlw b'111100' ; 3 retlw b'011001' ; 4 retlw b'101101' ; 5 retlw b'101111' ; 6 retlw b'111000' ; 7 retlw b'111111' ; 8 retlw b'111101' ; 9 ; Display digit passed in W on 7-segment display set7seg_R movwf digit ; save digit call get7sB ; lookup pattern for port B movwf PORTB ; then output it movf digit,w ; get digit call get7sC ; then repeat for port C movwf PORTC retlw 0 END