AR Timer as 25ms Timebase

powermac1 · ‎2007-01-15

Posted on January 16, 2007 at 07:11

powermac1 · ‎2007-01-04

Posted on January 05, 2007 at 06:41

Hello Folks,

i programmed the ART as freerunning Timer.

Fosc= 3,6864 MHz, ClkDiv= 3, Prescl= 128

Fin= 9600, RC= 10h

If my Calculations are correct, the above Settings = 25ms.

The Overflow Interrupt is used to update some Calcs(Tcyc.

As far as i know, ARTs need no additional cycles for INT and Reload.

They run and run until RESET. OK, the INTMASK must be written but

it have no effect on the running Timer. Hey, its Hardware.

Is it the same with the ST6265 ART. Or are there add. Cycles?

best regards

Andreas

powermac1 · ‎2007-01-15

Posted on January 16, 2007 at 07:11

Hi again,

there are ''dead'' cycles when using the ART as INT source.

To check this out, i programmed a simple software RTC using the

ART OverflowINT as Timebase.

Every INT increments a register til 40d. 25ms*40=1s.

result: the clock runs ahead.

question: WHY?

Andreas