Two PIA exceptions when using the PIA test EPROM

PIA 8H uses pins 2-9 as switch inputs, so ground every pin of CN10 with clip leads before probing those pins. PIA 11B has pin 9 tied to ground because it is unused, so it never toggles.

Systems

• Data East CPU Version 1/2
• Data East CPU Version 3
• Data East/Sega CPU Version 3b

Related tips

• CPU EPROM jumpers J4 and J5
• Test program does not run at all
• PIAs or the EPROM are never selected
• Program runs but the PIAs never respond
• CPU board PIA positions and jobs
• CPU jumpers J4 and J5 set the EPROM size at 5C
• Running the Data East test EPROM
• Data East CPU diagnostic test EPROM

Source: Repairing DataEast 1987 (Laser War) to Sega 1995 (Batman Forever), Part Two, Clay Harrell (pinrepair.com)