7485

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The 7485 (74LS85, 74HC85) is a digital magnitude comparator IC.

7485 Pinout

       .--\/--.
  B3 --+      +-- Vcc
IA<B --+      +-- A3
IA=B --+      +-- B2
IA>B --+  85  +-- A2
QA>B --+      +-- A1
QA=B --+      +-- B1
QA<B --+      +-- A0
 GND --+      +-- B0
       `------'

Signal descriptions

  • A3-A0: 4-bit number A
  • B3-B0: 4-bit number B
  • IA<B: Cascade from next lower nibble (use false for lowest)
  • IA=B: Cascade from next lower nibble (use true for lowest)
  • IA>B: Cascade from next lower nibble (use false for lowest)
  • QA<B: True if A < B, false if A > B
  • QA=B: False if A < B or A > B
  • QA>B: False if A < B, true if A > B

If A is not equal to B, the cascading inputs have no effect.

This IC has been proposed as the PRG ROM decoder for NROM-368.

References