[SOLVED] using timer registers.

[crazyramila]

hi im new to this subject,
i implmnt a small circuit using 16F877A


LIST p=16F877A
#include p16F877A.inc
__CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC & _LVP_OFF

STATUS equ h'03'
PORTA equ h'05'
TRISA equ h'85'

;*********shange the bank************
bsf STATUS,5
bcf PORTA,0
bcf STATUS,5

main
;*********bulb on*************
bsf PORTA,0

;*********bulb on*************
bcf PORTA,0

goto main
end



now i want to reduce the speed of this process without using delay loops
can any 1 help me to do that using TMRO.....?????

 

[cubanflyer]

how long for the delay off and on?
What speed is your pic running at?

This information is required to work out the prescalers of the TMR0.

 

[crazyramila]

30sec delay
n
speed 4MHz

---------- Post added at 15:31 ---------- Previous post was at 15:30 ----------

30sec delay
n
speed 4MHz

 

[cubanflyer]

Here is some code I will mod it in a short while for the delays, it will give you an idea of how to do it.

LED	equ 0x20	;variable for led
temp_s	equ 0x21
temp_w	equ 0x22


	goto start
	ORG 0x0004 


isr_routine
	movwf	temp_w		;save the contents of W
	movf	Status,W	;Move status to W	
	movwf	temp_s		;save the status register

;setup the next interrupt
	movwf	.99	
	movwf	TMR0

	movlw	b'1'		; here we xor the contents of LED and save
	xorwf	LED,1
	movfw	LED
	movwf	porta		;switch the led

ExitISR
	bcf		intcon,T0IF
	movf	temp_s,w
	movwf	status
	swapf	temp_w,f
	swapf	temp_w,w
	retfie

Start
	banksel	trisa
	clrf	trisa
	banksel	porta
	clrf	porta
	clrf	LED

;setup the interrupts
	movlw	b'10000001'		;set up prescaler etc
	banksel	trisa
	movwf	option_reg
	bsf		intcon,7
	bsf		intcon,5
	banksel	porta

doloop
	goto $
	

end

 

[crazyramila]

thank you for your prompt response
i really appreciate it