7432: Difference between revisions
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Gnd -- GND | Gnd -- GND | ||
For a discrete logic mapper, this can be used to provide a fixed bank at $C000 by overriding a [[74161]] latch output with ''CPU A14'' (e.g. [[UxROM]]). | For a discrete logic mapper, this can be used to provide a fixed bank at $C000-FFFF by overriding a [[74161]] latch output with '''CPU A14''' (e.g. [[UxROM]]). | ||
[[Category:7400 series|032]] | [[Category:7400 series|032]] | ||
Latest revision as of 23:14, 14 December 2022
The 7432 (variants 74LS32, 74HC32) is a 74-series logic IC with four independent 2-input OR gates.
7432 Pinout
.--\/--.
1A -> |01 14| -- +5V
1B -> |02 13| <- 4A
1Y <- |03 12| <- 4B
2A -> |04 11| -> 4Y
2B -> |05 10| <- 3A
2Y <- |06 09| <- 3B
Gnd -- |07 08| -> 3Y
`------'
Signal descriptions
For each set of pins starting with the same number, Y is high if either A or B are high.
Fixed Bank Implementation
7432 -- Connection ------------------ +5V -- +5V 01 -- CPU A14 02 -- 74161 Q0 03 -- PRG A14 = CPU A14 OR 74161 Q0 04 -- CPU A14 05 -- 74161 Q1 06 -- PRG A15 = CPU A14 OR 74161 Q1 09 -- CPU A14 10 -- 74161 Q2 08 -- PRG A16 = CPU A14 OR 74161 Q2 12 -- CPU A14 13 -- 74161 Q3 11 -- PRG A17 = CPU A14 OR 74161 Q3 Gnd -- GND
For a discrete logic mapper, this can be used to provide a fixed bank at $C000-FFFF by overriding a 74161 latch output with CPU A14 (e.g. UxROM).
