Prescaling the clock and creating a delay

[DaveRoberts]

Hello,

I am totally new to PICS and would like to create a time delay of between 5 or 10 seconds. Obviously with a clock speed of 3MHz a simple count is a big number. I am aware that the clock can be prescaled to give a 1:256 ratio meaning the count would be substantially less. The only problem is I do not know how to write the code for this. Can anyone help??

[Benj]

Hello

The easiest way to create a second delay is to create a function with a byte and an integer variable.

byte - inner_loop
int - outer_loop

then do something similar to the following.

for (outer_loop=0;outer_loop<3000;outer_loop++)
{
for (inner_loop=0;inner_loop<250;inner_loop++);
}

//Note this code is designed to work with a 3MHz crystal.

To create delays of more then one second simply add another for loop around the second delay structure.

If you need a very precise second timer then your better off using the Timer0 interrupt.

[KeithSloan]

For time delays in assembler I recommend PicLoops. It takes all the hardwork away http://www.mnsi.net/~boucher/picloops.html

Keith

[DaveRoberts]

This does not seem familiar to me. I did forget to mention that I am using the PIC16F84A. I assume the code you have sent me here is in C?

Dave

[Benj]

Hello Keith

That software looks great. Wish I had something like that back when I was writing assembler code.

[Benj]

Hello Dave

The example code that Keith sent is in assembler. It should work fine with MPLAB or other similar PIC compilers. It will also work with your 16F84A chip.