The 8255 Tester Board Upgrade Problem

The 8255 5 i/o upgaded board giving trouble today. The I/O were not in tally with the Intermediate Interface board (IIB). Troubleshoot and found out that the IIB configuration is not exactly the same as in the book as designed by the Taiwan group. Doublecheck with the one done by Mr Khow couple weeks ago. It doesnt match that one as well. Check the port 1 configuration and sketch the layout configuration for the IIB from the IDC 40P to the screw type connectors. Here is the layout found.


Later, connect the IIB to the 8255 5 I/O Tester Board. The connection failed as well where the 12VDC LED indicator is not light up. Check the upgraded PCB and found some wiring problem. Disconnect the upgraded part from the old 5 output ports. Test the old output port only. It's OK, meaning the trouble was caused by the upgraded circuitry.


Write simple program to use the input and output of the 8255. Test against IIB, and 8255 5O Tester Board. It can work but the program need to be fine tune to get more stable result.