How the switch matrix is scanned

RIOT U4 sends eight low-going strobes, repeated about every 10 ms, to the playfield and front door. They come back on eight return lines R0-R7 into U4 port A, together with the option switch returns. Any closure lasting 10 ms or more is recognized, and up to 15 repeat closures per switch can be queued.

Systems

• Gottlieb System 80
• Gottlieb System 80A

Related tips

• Where to see the switch matrix strobes
• Switch matrix connectors A1-J5 and A1-J6
• One or more playfield switches do nothing
• The slam input has priority over every other switch
• Switch test (step 18) shows switches closed
• A coin chute switch does not register or registers wrongly
• A playfield switch triggers the wrong response
• The play-test button will not start the test sequence

Source: System 80 Service Manual, Gottlieb