15th Apr 2021, 12:19 pm
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#1667
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Octode
Join Date: May 2012
Location: Perth, Scotland
Posts: 1,807
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Re: Non-working Commodore PET 3016
After the first POKE, all connections are 0.05V
After the second POKE, all connections are c. 3.25V with the exception of D which is c. 4.3V
Colin.
Quote:
Originally Posted by SiriusHardware
Right, so now do this bit suggested earlier.
and then measure the voltages on the IEEE port 1,2,3,4,A,B,C,D connections - all those lines should be 0V / logic 0.
If you then
and measure the voltages on pins 1,2,3,4,A,B,C,D again, all those lines should now be at logic 1 (~3V or greater).
If you get the voltages suggested, that will tell you that the port is working in output mode but not in input mode.
Generally speaking this is likely to be a problem with the MC3446 buffers, but we will also do checks to make sure it is not caused by UC6, depending on what the above checks find. |
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