simple delay for PIC16Fxx

[DrOohYen]

interrupt ใน pic16fxx คือ

Hi

Can Someone please explain me how to count a 1 ms delay for pic with 8 Mhz oscillator ? I mean what value i should put into TMRx register to acquire such a delay - and what prescaller (if needed ) should be used.

Thx in advance

 

[blueroomelectronics]

Here's the classic Delay Code Generator on PIClist



Here's the code it generated for your question

; Delay = 0.001 seconds
; Clock frequency = 8 MHz

; Actual delay = 0.001 seconds = 2000 cycles
; Error = 0 %

	cblock
	d1
	d2
	endc

			;1998 cycles
	movlw	0x8F
	movwf	d1
	movlw	0x02
	movwf	d2
Delay_0
	decfsz	d1, f
	goto	$+2
	decfsz	d2, f
	goto	Delay_0

			;2 cycles
	goto	$+1

Edit opps you want to use a timer. I'll see if I can dig some code up.

 

[gebepic]

reloadT1Hi equ 255
reloadT1Lo equ 6 ; trimming
count equ 0x20
org 0
goto setup
org 4
retfie
; 8 megs-->> one tick = 0.125 uSec
; prescale by 8 -->> 1 uSec / tick
setup movlw 00110000b;leave bit 0 = 0
movwf t1con
clrf count
; must preset High and Low
; must check interrupt flag(no need for interrupt)
; just the flag



loop
use bcf status,rp0 ; 1 make sure to be in the right bank
bcf pir1,tmr1if ; 1
movlw reloadT1Hi ; 1
movwf tmr1h ; 1
movlw reloadT1Lo ; 1
movwf tmr1l ; 1
bsf t1con,0 ; 1 from now on progr steps are not delays
testt1 btfss pir1,tmr1if
goto testt1
; timed out 1 usec for 8 ticks
incf count,f
goto loop

end

Just cooked this one

Note: You would need a Xtal to run at 8 megs on a 16F676

 

[sos]

for any uc set the prescale register than set the register to which it should matces(like match register) and see the clock parameter that which clock the timer is using.