Quote:
Originally Posted by ScottishColin
On the IEEE subject, is the code on page 184 of this PDF worth typing in to try?
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Sorry, I didn't notice that you had tried the super simple test I suggested earlier (The same test is buried in the start of that longer program, which is probably worth typing in and saving since you appear to have a working tape setup).
Anyway, the second result should be 255 (same as the number you wrote out in the second instance).
When you write out 255 (decimal) you are sending all 1s (11111111) to the output latches and when you PEEK the port you should see the same bit states coming back, but instead you are seeing 126 which is 01111110, suggesting a possible fault with bits 0 and 7 of the port.
Try that program and see what it reports. If it agrees there is a problem we'll drill down and find out whether the problem is with output to the port or readback from the port.
If you
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).