Posted on February 25, 2005 at 04:05Hi, Please help me, in our application, interrupt is forbidden to use for timer. And I must change the PA7 output every 500ms.
And the below is my program, my questions is that why when we test the software, it appears that timer A spend only 250us completing roll from 0xFFFD to 0x3CAC.In theory, it should be completed in 50ms.
void main(void)
{
ResetTimer();
TimerCounter=0;
//--Read from SPI forever ---------------------
do
{
GetTimer();
}while (1);
return; // never go here, for lint
}
void ResetTimer(void)
{
U8 temp=0;
/*
** Disable all interrupt of timer A
** Disable output compare and input capture mode
** Disable PWM and one pulse mode.
*/
TACR1 = 0x00;
/* Set Timer frequency to fosc/8*/
TACR2 = 0x08;
/*Set the timer enable*/
TACSR = TACSR & 0xFB ;
/*See if TOF is set, this means that timer over flow then clear the TOF*/
if (TACSR && 0x20)
{
temp=TACSR;
temp=TACLR;
}
/*Reset the timer counter to FFFC*/
TACHR = 0xFF;
TACLR = 0xFC;
return;
}
void GetTimer(void)
{
U16 CurrentTimer;
U8 temp;
/*Get the timer A value*/
CurrentTimer= (TACHR * 0x100) + TACLR;
/*Check if timer A has run 50 ms*/
if (CurrentTimer<=0x3CAC)
{
TimerCounter = TimerCounter + 1;
/*If program has run over 500 ms, then switch the PA7 status*/
if (TimerCounter >= 10)
{
/*switch the PA7*/
temp = PADR;
temp = (((temp & 0x80) ^ 0x80) & 0x80) | (temp & 0x7F) ;
PADR = temp;
TimerCounter=0;
}
ResetTimer();
}
return;
} :o
