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Not being able to test 82c55a
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gkmaia:
Having a hard time to test a 82c55a.

I am following the truth table but I can only send data from the ports to the data bus. And not being able to send the data from data bus to ports.

I am attaching A0,A1,CS,RD & WR directly to gnd OR VCC as required by the table and sending 5v pkpk signals from and to ports/bus.

What am I missing here?
MK14:
What about the RESET pin ?
DrG:

--- Quote from: gkmaia on August 02, 2020, 09:39:36 pm ---Having a hard time to test a 82c55a.

I am following the truth table but I can only send data from the ports to the data bus. And not being able to send the data from data bus to ports.

I am attaching A0,A1,CS,RD & WR directly to gnd OR VCC as required by the table and sending 5v pkpk signals from and to ports/bus.

What am I missing here?

--- End quote ---

Have you reviewed the modes and set them as you intended and using the correct ports for the mode? https://ekoharsono.files.wordpress.com/2012/10/5-82c55-programmable-peripheral-interface1.pdf?

[*dayam* I have not thought about that chip in many years.]
gkmaia:
Yes. I am using it as Mode 0 port A B or C. CS A0 and A1 LOW.

I am not going down A0 and A1 HIGH and using the control register.

Just basic data to and from ports flow.

RESET pin is LOW. But it actually does not make a difference when I change it.
DrG:
circuit? code?
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