Author Topic: 89C668 reluctant to run user code  (Read 3131 times)

david fussell

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89C668 reluctant to run user code
« on: April 06, 2004, 05:06:16 am »

I'm happy to say that I can reliably enter ISP mode, and can re-program the '668 device repeatedly with no problem, so please excuse the slightly off topic subject, but I was hoping someone may have experienced this before:

The problem I have is that it's a bit variable as to what is happening upon non-ISP mode startup- The user code (currently just flashing led's ) sometimes runs straight away, but usually there's no activity for a minute or so before the user code runs.

I'm suspicious that the PC may not be getting set to 0x0000 upon power up, but asserting a reset (RC) during this minute of 'idle' time has no apparent effect. During execution of user code however, the reset works fine.

...all supplies and signals appear clean.

Any suggestions?



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Re: 89C668 reluctant to run user code
« Reply #1 on: April 06, 2004, 12:45:10 pm »
     I've been using the 89c668 for a while now. If I were you I would disable
interrupts to start with.  Try to toggle a port pin low and look at it with a scope,forget about your led's for now. Sounds like you are almost there.