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interrupt 5us with a 16f877

 
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lazzy



Joined: 05 Sep 2005
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interrupt 5us with a 16f877
PostPosted: Mon Sep 05, 2005 3:56 am     Reply with quote
I want to create a interrupt timer 1 -5us

could you help me ?
Ttelmah
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PostPosted: Mon Sep 05, 2005 4:25 am     Reply with quote
Forget it.
The chip is just not capable of this sort of speed. You might just be able to 'bodge' something, using assembler, but you are not going to be able to do anything else (so there is no point in using an interrupt). The fastest version of this chip, clocks at 20MHz. This give 5 instructions in a 1uSec period, or 25 in a 5uSec period. The typical interrupt handler will involve 50 instructions in saving registers and restoring them, plus how ever many are needed for the code itself.
If you just need to 'time' something, look at the CCP modules, which are designed to do exactly this in hardware.

Best Wishes
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