 | Hi,
Im working on a project involving the AT91rm9200. Im trying to generate
interrupts through the System Timer`s Periodic Interval Timer. Its not
working the way i want it to. Im getting periodic interrupts all right,
but im not able shut it off properly. I keep getting timer interrupts
continuously..the code of my C interrupt handler is below: (as may be
evident, im using atmel`s pre-canned asm routines in the file irq.mac
for backstage interrupt handling, but the C routines are mine )
void timer_c_irq_handler()
{
//Dummy variable used for clearing ST_SR
volatile int status;
AT91PS_ST pST =3D AT91C_BASE_ST;
//read ST_SR
status =3D pST->ST_SR;
//clear the interrupt for re-use
AT91F_AIC_ClearIt( AT91C_BASE_AIC,AT91C_ID_SYS );
//Disable interrupts by the timer
//AT91F_ST_DisableIt( AT91C_BASE_ST, AT91C_ST_PITS );
AT91F_DBGU_Printk("\n\rSystem Timer interrupt..\n\r");
}
As u can see, im trying to clear the ST_SR registe`s PITS bit by
reading it after the interrupt has occured..this is because the manual
says:
=B7 PITS: Period Interval Timer Status
0 =3D The period interval timer has not reached 0 since the last read of
the Status Register.
1 =3D The period interval timer has reached 0 since the last read of the
Status Register.
So shouldnt PITS go to 0 if i read it again in the irq handler above,
and stop bothering the AIC? Everything works fine if i uncomment the
"DisableIt" function call, but just want to be clear about where im
going wrong.
Thanx in anticipation
Mayank
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