jitter - when using Outout compare/pwm

[adi2]

Posted on November 18, 2003 at 13:29

jitter - when using Outout compare/pwm

[adi2]

Posted on November 18, 2003 at 13:29

hi !

i'm using the st72264 with the in dart and i encounter jitter which is un acceptional while using output compare function or even the PWM

function.

i measure time and when the time is over i toggle a pin (PB2) with a desire fix frequency.

the jitter comes up every time the S/W has to deal with the toggle of the pin, let me explain, when i use the PWM function with OLV1 != OLV2 i get a fixed no jitter signal, but when i use the INT for toggling the bit (and with output compare )a jitter appears.

i added the basic application :

void main(void)

{

PBDDR = 0xFF;

PBOR = 0XFF; //

/* PORTS_Init(); // init ports */

ClrBit(PADDR,5); // set Port A, 5 and 7 pins as floating input

ClrBit(PADDR,7);

ClrBit(PAOR,5);

ClrBit(PAOR,7);

PCDDR |= 0x04;

PCOR |= 0x04;

MISCR1 |=0x20;

/* using the output compare */

TBCLR = 0 ; // reset the counter

TBCR1 = OCIE ;

TBCR2 = Fcpu8 ;

TBOC1HR = 0;

TBOC1LR = 100;

asm (''rim'');

while(1) {

}

} // main loop

interrupt 8 void TIMER_B_INT (void)

{

unsigned char temp=0;

asm (''sim'');

temp=TBSR;

if (temp & OCF1)

{

TBCLR = 0 ; // reset the counter

TBOC1HR = 0;

TBCR1 = OCIE ;

TBCR2 = Fcpu8 ;

TBOC1LR = 100;

if (ValBit(Data,j))

PBDR|=0x04;

else

{

PBDR &= 0b11111011;

}

j++;

if (j==9)

j=1;

}

asm (''rim'');

}

and i attached an oscilloscope picture,

what could be the problem ???????

adi.

[ This message was edited by: Bamba on 18-11-2003 18:01 ]

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Attachments :

TEK00001.PCX : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I08u&d=%2Fa%2F0X0000000bVh%2FquSf7QdXgWF0A1PpSkfjJYq17BKWDOztJJCH1e30fBc&asPdf=false