9S12E - Can you drive the external reset pin with software?

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9S12E - Can you drive the external reset pin with software?

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Beaker
Contributor I
Due to the EOL of the Intel 87C196KC, I am redesigning our controllers with the MC9S12E64.  In our application, the 87C196KC was the reset master in our multi-processor system.  I need a way of driving the external reset pin based on various conditions.
 
I believe I can generate an immediate reset by enabling the COP watchdog and then writing garbage (not 0x55 or 0xAA) to the ARMCOP register.  Does this also drive the external reset pin?
 
Thanks -
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Alban
Senior Contributor II
Yes internal resets do drive the pin low.
Duration is available in the graph of the CRG (Clock and Reset Generation) module.
It shows the 128 cycles + 64 cycles released to see if it is internal or external reset.
 
Alban.
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Beaker
Contributor I
Thanks for the quick reply.
 
I thought I had read all the pertinent sections in the data sheet, but I somehow missed the obvious paragraph about this in section 4.5.
 
COPCTL = 0x01;    // Enable the COP
ARMCOP = 0xFF;   // Force a COP reset
 
With our clock setup the above code gives me a nice ~17usec reset pulse with is enough to reset the other processor in our system.
 
I'm guessing that if you have an external reset / voltage monitor on the line which extends the pulse, you will always go to the external reset vector instead of the COP reset vector 
 
Thanks again.
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