To: mas863@media.mit.edu
Subject: delay code

Hi, I wrote a little routine to delay for some number of milliseconds. I thought other people might want to use it. The code is below. Before calling this routine, set W to the number of milliseconds you want to delay. for instance:

	MOVLW	250
	CALL	delay_ms

to delay for 250ms = 1/4 second. For times greater than 255ms you'll need to call it multiple times. I can modify it for 10ths or 100th of a second, or microseconds if people want. This routine assumes a 20MHz clock. If you have a differently valued crystal, it won't work for you. This isn't for exact timing, it is an aproximate but should be pretty close. If your program already uses memory locations 30h and 31h, just change the EQU's at the beginning.


; --- Delay Routine ---
; written by bb2 on 11/6
; input: delay aprox. W ms
; req: for 20 MHz clock only

_DELAY_PARAM EQU 0x30
_DELAY_COUNT EQU 0x31
delay_ms:
	MOVWF	_DELAY_PARAM
_delay_loop_1:
	MOVLW	d'227'
	MOVWF	_DELAY_COUNT
_delay_loop_2:
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	NOP
	DECFSZ	_DELAY_COUNT
	GOTO		_delay_loop_2
	DECFSZ	_DELAY_PARAM
	GOTO		_delay_loop_1
	RETURN