; ------------------------------------------------------------------------ ; ; Title: ; ; PD59 -- PIC 10 MHz to 1/2/5/10 x 1/10/100/1000 ms pulse generator ; ; Function: ; ; This PIC program implements a digital frequency divider: cpu hardware ; and isochronous software divide the input clock by a factor of ; 10 thousand to 100 million, dynamically selectable by the user. ; ; Given a 10 MHz input clock, 4 binary configuration pins select ; one of 13 different output frequencies from 1 kHz to 0.1 Hz, ; having periods from 1 ms to 10 s, in 1-2-5 steps. ; ; Ground config pins as necessary to select 0000 to 1111 in binary. ; - the high 2-bits select period x1, x10, x100, x1000 ; - the low 2-bits select period x1, x2, x5, x10 ; ; Diagram: ; ---__--- ; 5V (Vdd) +++++|1 8|===== Ground (Vss) ; 10 MHz clock in ---->|2 pD 7|<+--- Config1 ; frequency out <----|3 59 6|<+--- Config2 ; Config8 o--->|4 5|<+--- Config4 ; -------- ; Notes: ; ; o External pull-up required on pin4/GP3. ; + Config inputs (pin7/GP0, pin6/GP1, pin5/GP2) have internal WPU. ; Output frequency accuracy is the same as clock input accuracy. ; Output drive current is 25 mA maximum per pin. ; Coded for Microchip 12F675 but any '609 '615 '629 '635 '675 '683 works. ; ; Version: ; ; 25-May-2025 Tom Van Baak (tvb) www.LeapSecond.com/pic ; ; ------------------------------------------------------------------------ ; Microchip MPLAB IDE assembler code (mpasm). list p=pic12f675 include p12f675.inc __config _EC_OSC & _MCLRE_OFF & _WDT_OFF ; Register definitions. cblock 0x20 ; define register base gpcopy ; shadow of output pins endc ; One-time PIC 12F675 initialization. org 0 ; power-on entry bcf STATUS,RP0 ; bank 0 movlw 0x07 ; turn comparator off movwf CMCON ; clrf GPIO ; set output latches low bsf STATUS,RP0 ; bank 1 errorlevel -302 clrf ANSEL ; all digital (no analog) pins movlw ~(1< W movwf GPIO ; W -> output pin(s) ; Make loop overhead a convenient 1000 cycles. movlw d'9' ; call DelayW100 ; delay W*100 movlw d'84' ; call DelayW1 ; delay (15 <= W <= 255) ; Query config bits to determine loop period. ; Config pins default to 1, tie to ground for 0 ; 16-entry jump table is 0000 ... 1111 movf GPIO,W ; get config bits andlw 0xF ; 4-bits addwf PCL,F ; jump PCL+W (computed goto) goto do_10s ; 10 MHz -> 0.1 Hz, 10 s goto do_5s ; 10 MHz -> 0.2 Hz, 5 s goto do_2s ; 10 MHz -> 0.5 Hz, 2 s goto do_1s ; 10 MHz -> 1.0 Hz, 1 s goto do_1s ; 10 MHz -> 1 Hz, 1000 ms goto do_500ms ; 10 MHz -> 2 Hz, 500 ms goto do_200ms ; 10 MHz -> 5 Hz, 200 ms goto do_100ms ; 10 MHz -> 10 Hz, 100 ms goto do_100ms ; 10 MHz -> 10 Hz, 100 ms goto do_50ms ; 10 MHz -> 20 Hz, 50 ms goto do_20ms ; 10 MHz -> 50 Hz, 20 ms goto do_10ms ; 10 MHz -> 100 Hz, 10 ms goto do_10ms ; 10 MHz -> 100 Hz, 10 ms goto do_5ms ; 10 MHz -> 200 Hz, 5 ms goto do_2ms ; 10 MHz -> 500 Hz, 2 ms goto do_1ms ; 10 MHz -> 1000 Hz, 1 ms ; 1 ms period is 0.5 ms toggle is 1250 cycles (-1000 = 250) do_1ms: nop ; movlw d'250' ; call DelayW1 ; delay (15 <= W <= 255) goto loop ; 2 ms period is 1 ms toggle is 2500 cycles (-1000 = 1500) do_2ms: nop ; movlw d'15' ; call DelayW100 ; delay W*100 goto loop ; 5 ms period is 2.5 ms toggle is 6250 cycles (-1000 = 5250) do_5ms: movlw d'52' ; call DelayW100 ; delay W*100 movlw d'50' ; call DelayW1 ; delay (15 <= W <= 255) goto loop ; 10 ms period is 5 ms toggle is 12500 cycles (-1000 = 11500) do_10ms: nop ; movlw d'115' ; call DelayW100 ; delay W*100 goto loop ; 20 ms period is 10 ms toggle is 25000 cycles (-1000 = 24000) do_20ms: nop ; movlw d'240' ; call DelayW100 ; delay W*100 goto loop ; 50 ms period is 25 ms toggle is 62500 cycles (-1000 = 61500) do_50ms: movlw d'6' ; call DelayW10k ; delay W*10000 movlw d'15' ; call DelayW100 ; delay W*100 goto loop ; 100 ms period is 50 ms toggle is 125000 cycles (-1000 = 124000) do_100ms: movlw d'12' ; call DelayW10k ; delay W*10000 movlw d'40' ; call DelayW100 ; delay W*100 goto loop ; 200 ms period is 100 ms toggle is 250000 cycles (-1000 = 249000) do_200ms: movlw d'24' ; call DelayW10k ; delay W*10000 movlw d'90' ; call DelayW100 ; delay W*100 goto loop ; 500 ms period is 250 ms toggle is 625000 cycles (-1000 = 624000) do_500ms: movlw d'62' ; call DelayW10k ; delay W*10000 movlw d'40' ; call DelayW100 ; delay W*100 goto loop ; 1 s period is 0.5 s toggle is 1250000 cycles (-1000 = 1249000) do_1s: movlw d'124' ; call DelayW10k ; delay W*10000 movlw d'90' ; call DelayW100 ; delay W*100 goto loop ; 2 s period is 1.0 s toggle is 2500000 cycles (-1000 = 2499000) do_2s: movlw d'249' ; call DelayW10k ; delay W*10000 movlw d'90' ; call DelayW100 ; delay W*100 goto loop ; 5 s period is 2.5 s toggle is 6250000 cycles (-1000 = 6249000) do_5s: movlw d'250' ; call DelayW10k ; delay W*10000 movlw d'250' ; call DelayW10k ; delay W*10000 movlw d'124' ; call DelayW10k ; delay W*10000 movlw d'89' ; call DelayW100 ; delay W*100 movlw d'97' ; call DelayW1 ; delay (15 <= W <= 255) goto loop ; 10 s period is 5.0 s toggle is 12500000 cycles (-1000 = 12499000) do_10s: movlw d'250' ; call DelayW10k ; delay W*10000 movlw d'250' ; call DelayW10k ; delay W*10000 movlw d'250' ; call DelayW10k ; delay W*10000 movlw d'250' ; call DelayW10k ; delay W*10000 movlw d'249' ; call DelayW10k ; delay W*10000 movlw d'89' ; call DelayW100 ; delay W*100 movlw d'95' ; call DelayW1 ; delay (15 <= W <= 255) goto loop include delayw.asm ; precise delay functions end