delay routine

        radix   dec
clock   equ     8               ; user clock frequency in MHz
usecs   equ     clock/4         ; cycles/microsecond multiplier
msecs   equ     usecs*1000      ; cycles/millisecond multiplier

DelayCy macro   pDelay          ; cycles (Tcy), minimum 16
        local   cycles
        cycles = pDelay
     while cycles > 262032
        movlw   high((262016-16)/4)+1
        movwf   TMRH
        movlw   low((262016-16)/4)
        call    DelayLo-(262016%4)
        cycles -= 262016
     endw
        movlw   high((cycles-16)/4)+1
        movwf   TMRH
        movlw   low ((cycles-16)/4)
        call    DelayLo-(cycles%4)
        endm[COLOR=Red]
;                                                                 *
;  example code for simulation testing;                           *
;                                                                 *
SimTest DelayCy(1000*msecs)     ; 1 second delay
        nop                     ; put simulator break point here[/COLOR]
;                                                                 *
;  Delay(16..262159 Tcy) subroutine   Mike McLaren, K8LH, Jun'07  *
;                                                                 *
;  12 words, 1 RAM variable, 14-bit core                          *
;                                                                 *
Delay.16
        nop                     ; entry point for delay%4 == 3    |B0
        nop                     ; entry point for delay%4 == 2    |B0
        nop                     ; entry point for delay%4 == 1    |B0
DelayLo addlw   -1              ; subtract 4 cycle loop time      |B0
        skpnc                   ; borrow?  yes, skip, else        |B0
        goto    DelayLo         ; do another loop                 |B0
        nop                     ;                                 |B0
DelayHi addlw   -1              ; subtract 4 cycle loop time      |B0
        decfsz  TMRH,F          ; done?  yes, skip, else          |B0
        goto    DelayLo         ; do another loop                 |B0
        goto    $+1             ; burn off 2 cycles               |B0
        return                  ;                                 |B0
;

loop
        bcf     PORTC,0         ; turn on LED on RC0
        DelayCy(500*msecs-1)    ; delay 500 msecs minus 1 cycle
        bsf     PORTC,0         ; turn off LED on RC0
        DelayCy(500*msecs-3)    ; delay 500 msecs minus 3 cycles
        goto    loop            ; loop forever