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'Problem with PIC16C74A'
1999\10\07@060356 by Peter Grey

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I have a problem when using the Timer 0 function and having an external
clock (RA4). I find that there is a timer 0 interrupt although T0IE is set
to zero. I am using an emulator so can see the registers ok. The target
board also acts as though there is an interrupt. I can insert breakpoints
and see that there is in fact an interrupt on timer 0 and also that T0IE is
not set. Has anyone seen something like this??

TIA

Peter Grey

1999\10\07@075710 by Steve Kelley

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Peter . . . .
Is the system actually interrupting and branching to the  * interrupt vector 0x04 * ?
Or . . . .are you just seeing the TMR0 interrupt flag being set ?   The interrupt flag
for TMR0 , will be set on an overflow , regardless of the state of any of the * enable *
flag bits.  But , shouldn't branch unless enabled . . . . . . we will wait to hear back . . .

Regards . . . .
                       Steve Kelley

{Original Message removed}

1999\10\07@095900 by Martin SchŠfer

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Hi Peter,

I don't know any problem with the timer interrupt. Please check, after the ISR
is entered, if any other IF is set.
If you use an emulator, disable all interrupts (GIE) from start (no toggling of
GIE in the program) and set a break on address 0x0004. I believe that the
emulator never stops.

Peter Grey schrieb:

{Quote hidden}

1999\10\07@191819 by Peter Grey

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At 05:55 AM 7/10/99 -0500, you wrote:
>Peter . . . .
>Is the system actually interrupting and branching to the  * interrupt
vector 0x04 * ?
>Or . . . .are you just seeing the TMR0 interrupt flag being set ?   The
interrupt flag
>for TMR0 , will be set on an overflow , regardless of the state of any of
the * enable *
>flag bits.  But , shouldn't branch unless enabled . . . . . . we will wait
to hear back . . .
>
>Regards . . . .
>                        Steve Kelley

Steve,

The T0IF flag gets set which I expect but it also branches to the interrupt
routine. I have used teh 16C74A quite a lot but never with this mode and
have had no problems. I just wonder if anyone has used this mode on a 74A.

Thanks,


Peter

>
>{Original Message removed}

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