Verifying Galaga 74LS259 CPU 3C
for your Galaga video game
Computer Aided Testing System

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The 259 chip controls reset / interrupt operations for the 3 CPU's to function together.

The 74LS 259 chip located at position 3C on a Galaga CPU can be tested in its entirety by test numbers 0114 through 0121 from the Galaga Test Table. Tests from this group initiate a "loop" condition, procedures in these tests include the watchdog reset pulse, as not doing so will not allow the 74LS259's outputs to be programmed, they will reset back to zero.

0112 00000000000000010002 Load 3C pin 14 N/a        pin_14_3c.gls  external measurement req 0113 00000000000000010002 Load 1P pin 11 N/a        pin_11_1p.gls  external measurement req 0114 00000000000000010002 Load 3C pin 4 (IRQ1)      pin_4_3c.gls   external measurement req 0115 00000000000000010002 Load 3C pin 5 (IRQ2)      pin_5_3c.gls   external measurement req 0116 00000000000000010002 Load 3C pin 6 (NMI)       pin_6_3c.gls   external measurement req 0117 00000000000000010002 Load 3C pin 7 (RESET)     pin_7_3c.gls   external measurement req 0118 00000000000000010002 Load 3C pin 9 (nofunc)    pin_9_3c.gls   external measurement req 0119 00000000000000010002 Load 3C pin 10 (MOD 0)    pin_10_3c.gls  external measurement req 0120 00000000000000010002 Load 3C pin 11 (MOD 1)    pin_11_3c.gls  external measurement req 0121 00000000000000010002 Load 3C pin 12 (MOD 2)    pin_12_3c.gls  external measurement req

An Example of processing these tests.

Contact me at greg@gls1electronics.com for more information regarding Galaga board repair.