> The main problem I have at present is in programming a delay.

The general method is to increment (or decrement) a counter for a 
specified number of counts. Nesting several counters helps give long 
delays. If using interrupts (and ultimately all paths lead to 
interrupts) you can manage a multibyte counter or nest of counters 
within the ISR (Interrupt Service Routine).

eg for a 100 uS interrupt a simple minded but usable delay routine 
might be.

Here_on_interrupt
....
inc 100_uS_Counter
IF 100_us_Counter = 100
     100_uS_Counter = 0
     inc 10_mS_Counter
     IF 10_mS_Counter = 100
        10_mS_Counter = 0
        inc seconds_counter
     ENDIF
ENDIF

This gives you nice decimal submultiples of a second in 2 decade steps 
(1, .01, .0001 increments) but is less memory efficient than letting 
each register overflow

______________________

You could look at the PICList site, which is sure to have a few 
zillion examples, but, as often, Google is your friend.

Googles ...

            PIC delay

I'm astounded at how good the first few hits are!

Mark's project page, time delays:

        http://www.mhennessy.f9.co.uk/pic/time_delays.htm

Going back to the start of the tutorial will probably be useful

        http://www.mhennessy.f9.co.uk/pic.htm

And
Delay code generator
On the PICList site as above ;-)

        http://www.piclist.com/techref/piclist/codegen/delay.htm

    For 5 seconds using specified registers, gives

; Delay = 5 seconds
; Clock frequency = 4 MHz

; Actual delay = 5 seconds = 5000000 cycles
; Error = 0 %

	cblock
	d1
	d2
	d3
	endc

Delay
			;4999993 cycles
	movlw	0x2C
	movwf	d1
	movlw	0xE7
	movwf	d2
	movlw	0x0B
	movwf	d3
Delay_0
	decfsz	d1, f
	goto	$+2
	decfsz	d2, f
	goto	$+2
	decfsz	d3, f
	goto	Delay_0

			;3 cycles
	goto	$+1
	nop

			;4 cycles (including call)
	return

___________________

Also, PIC delay loop calculator

        http://interaccess.org/arg/arg-list/msg00462.html




        Russell McMahon


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