Afternoon all,

I fear this is a very stupid question, sorry :)

Sadly, my MAX488E chip isnt working with my PIC16C74A. I'm almost certain the problem is something to do with internal pullup resistor on the PortB input that the RO line from the Max488e is connected to. The RO line into the PIC is never going high.

Data transfer (PIC->Max488->Max488->PIC) works when RO from the Max488 is connected to an input on PortA, without any pullup resistor (although the input is then floating when it should be low).

Basically I can use PortB and get a proper 'low' state but an invalid 'high' state, or use PortA and get the opposite.

Should it be possible to wire up a Max488 directly to a PIC? (I assumed it would be simply because the PCB I'm using has been designed by someone who obviously thought you should be able to) If this is not the right way to go about things, does anyone got a simple circuit diagram showing how it should be done?

Thanks,

Chris.

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