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S08PA32 IRQ and reset on the same pin

Question asked by Markku Rönö on Aug 21, 2015
Latest reply on Aug 25, 2015 by Markku Rönö

We're planning to use the MC9S08PA32 in a new revision of a product that currently has a GT32 in it.

I'm currently checking the differences of the micros to get an idea of the software porting work required.


One thing I noticed was that on the PA32 IRQ and reset are on the same pin. Reading the manuals I learned that I need to disable the reset in software to use the IRQ functionality.

But if I connect an external signal to to IRQ/Reset pin, how can I ensure that the software has enough time at power-up to disable the reset? In my case the external signal would be the PPS signal from a GPS module. If the GPS module starts up faster than the micro, it will drive the PPS line low. Wouldn't this keep the micro in reset permanently? Also, if the micro resets for some reason while the GPS module keeps running, wouldn't that cause a similar issue?


I tried searching the forums, but found nothing on this issue. That makes me think there is some simple way to deal with this scenario, but I'm just not seeing it. I hope someone here can enlighten me.



Best Regards,

Markku Rönö