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Old 14th Apr 2021, 6:45 pm   #1638
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,482
Default Re: Non-working Commodore PET 3016

Well, now that you are able to issue BASIC commands you can try these for a first-line check of the IEEE 488 port. This port is probably only important if you plan to acquire a disc drive or something which pretends it is one, such as the SD2PET.

Notice the POKE address is slightly different to the PEEK address in both cases.

Code:
POKE 59426,0
PRINT PEEK(59424)
Result=?

Code:
POKE 59426,255
PRINT PEEK(59424)
Result =?

The IEEE port has an unusually useful structure in so far as the state of the output latches can be read by the input buffers, so you can write a value to the 8 data bits of the IEEE port and read that value back, in the process proving both the output latches and the input buffers - provided the value you read back in is the same as the value you wrote out.
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