7432

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).