Lpc2000

---- Original Message ----
From: "ylavoie66" <ylavoie66@...>
To: <lpc2000@yahoogroups.com>
Sent: Saturday, May 13, 2006 4:59 AM
Subject: [lpc2000] Timer interrupts on LPC2138

> Has anyone ever experienced a similar problem with timers on the
> LPC2138?
>
> I want to get a timer to generate an interrupt at every 1ms (system
> tick).  I configured the prescaler so the timer would count with a 1ms
> period, and the match register set so the timer would generate an
> interrupt every 1ms.
>
> This resulted in a 2ms system tick ??!!
>
> As a test, I changed my prescaler, so the counter would count on a 1us
> period, and interrupt every 1000us, which is the same as 1mm here in
> Canada :)
>
> I am still waiting for an answer from Philips, but it seems that
> setting a match of "1" is not working properly...

You should set the match register to one less than the desired period.  The
timer goes to 0 the next count _after_ the match, so if you set the match
register to e.g. 4, the timer will count 0, 1, 2, 3, 4, 0, 1, 2, 3, 4...
giving a period of 5.  Try a match value of 0.

Karl Olsen