Code Warrior V5.1 for 9S08QG8- inaccurate 1mS interrupt - Processor Expert

[stevec]

I have set up a 1mS interrupt using the Device Initialisation. I have checked that the trim value is being programmed by the programmer and copied to the trim registers by the program (again done by Device Initialisation). I am seeing an interrupt period of 1.08mS instead of 1mS. The only piece of code I have hand written is three lines in the interrupt routine which reset the interrupt flag and toggles and o/p line.
The Init_TPM bean parameters are
    Clock Source - bus rate clock
    Prescaler 1
    Modulo count = 105c
    (which gives) Period 1mS

    Overflow Int enabled

I must admit to not quite having a handle on the clocking sources yet which is why I've relied on the Device Initialisation function to get me started. Any ideas as to why I'm getting this discrepancy. I've checked the Multilink settings (Advanced Options) for  Trim Programming and the box is ticked.

Regards,

Steve


Message Edited by Alban on 2007-05-10 01:11 PM

[Alban]

Hi,

Just to let you and other readers know.
I added Processor Expert in the subject line.
Their official support is lurking in these Forums and it makes it obvious to everyone, including them.

Cheers,
Alban.

[peg]

Hi,

If we are leaving this for a Processor Expert expert, perhaps they can answer this.

How does PE arrive at the value of $105C for a 1ms delay with a QG default clock setup?

See also this thread:

http://forums.freescale.com/freescale/board/message?board.id=8BITCOMM&message.id=5903

[Curt]

Hi stevec, peg, bigmac et al

Following peg's note, maybe we should be asking what kind of timing tolerance can we expect from these devices in general over a reasonable  range of temperature and

supply voltage?  My hunch would be that 6% or so is not too bad, all things considered.  Just don't try to build a stop watch

By the way stevec -- appreciate your threads.  I seem to be having all the same problems you've had, but about a month AFTER you've had them -- so have learned

a lot from your conversations here!

[peg]

Hi Curt,

No. 6% is bad. This would mean serial connections would be dodgy.

You can trim to under 1% and then this should hold to 1%ish from there with temp over life. Voltage should remain the same in the one device.

Message Edited by peg on 2007-05-11 10:21 AM

[stevec]

Thanks for the replies guys.
This problem seems to be dealt with on two threads. Sorry about that. Perhaps better to keep the one on the 8-bit forum. I'm still at a bit of a loss as to the source of the problem. I've sent in a Service Request to Freescale as they have a Processor Expert section. As the product is very early in its design cycle its not an issue yet but has to be resolved before production.

Steve