Timers

[mitchf14]

I need some help with the hardware timers I'm using pic16f873 with a 20 MHz crystal, how could i create the same simple program below with a hardware timer i want a 10 second pause in between. The program is very simple example to help me learn to use the timers. thank you


Start

portb.2 = 1

pause 10000

portb.3 = 1

End

[Charles Linquis]

The "generic" way is to

Figure out the maximum "length" of the timers (use Mr. E's Multi-Calc).
Pick an appropriate timer and prescaler.
Figure out what the pre-load count should be for the time interval you need based on the timer, prescaler and oscillator.

The counter will increment from the pre-load value and when it reaches maximum count (0xFFFF for a 16 bit counter), it will set the timer's overflow flag bit (INTCON.2 in the case of TMR0).

So to intialize:

Load the counter with the pre-load count
clear the timer overflow flag bit
enable the timer

Then --



Top_Of_Main_program:

do some stuff here

IF INTCON.2 THEN ; the bit is set, so overflow has occurred.
TMR0H = HighByte of preload value
TMR0L = LowByte of preload value ; the order is important!
INTCON.2 = 0 ; Clear the flag bit
;Do what you want here when the timeout value is reached.
ENDIF


Goto Top_Of_Main_program

[mitchf14]

Thanks for the reply i will try that out.