10ms
20ms
50ms
100ms

16F877A running at 20MHz

I am using this now, but I am a little dubious, after the first cycle of
231, the outer loop overflows to 255, firing up the
osciliscope.

; --------------------------------------------------------------------------
----------------------------
; Delay routines - 20 MHz xtal
; --------------------------------------------------------------------------
----------------------------
Delay255
		movlw	0xff	;delay 255mS
		goto	d0
Delay100
		movlw	d'100'	;delay 100mS
		goto	d0
Delay50	movlw	d'50'	;delay 50mS
		goto	d0
Delay20	movlw	d'20'	;delay 20mS
		goto	d0
Delay10	movlw	d'10'	;delay 10mS
		goto	d0
Delay1	movlw	d'1'	;delay 1mS
		goto	d0
Delay5	movlw	0x05	;delay 5ms
d0		movwf	count1
d1		movlw	0xE7	; E7 = 231 decimal
		movwf	counta	; outer loop - delay 231 cycles
		movlw	0x04	; delay - 4 loops
		movwf	countb  ; total loop = 199 x (4+1) = 995 ( 4MHz 199 decimal x 5 =
995 )
Delay_0	decfsz	counta, f
		goto	$+2
		decfsz	countb, f
		goto	Delay_0
		decfsz	count1	,f
		goto	d1

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
Of Jan-Erik Soderholm
Sent: Wednesday, 5 January 2005 8:30 PM
To: piclist@mit.edu
Subject: RE: [PIC] 16F877A delay code


> Can someone help me with some delay code for a uP running at 20 MHz ?
> I have some code for 4MHz, is it just a matter of scalling by 5 ?

Hi.
How long delay ?
How often should this delay "run" ?

Generaly speaking, use timers for delays, not code.

Regards,
Jan-Erik



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