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Question & Answer
Classification:
Date: May 30, 2001
Disabling the 8031 microcontroller
Q:
Does anyone have experience on how to disable the 8031 such that the pins to the 8031 can be used for external devices on the x40-boards? In the xess-8031-documentation are the following comments:
The 8031 can be prevented from having any effect on the rest of the circuitry by forcing the RST pin high. When RST is active, most of the 8031 pins are weakly pulled high.
In the 8031-documentation from Intel I found:
A logic high on the reset-pin for two machine cycles while the oscillator is running resets the device.
Do you have to combine both the RST -pin should be high and XTAL1 should be connected to a clock signal? Is it really necessary to connect a clock to XTAL1 or are other signals necessary?
A:
The 8031 is already disabled. For default it does not work unless you use an property circuit (see An-103100-ucfpga.pdf). If you want to force a reset anyway, just alocate an VCC to pin 36, that is the 8031 RST pin, and it will work.