7485

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

7485 Pinout

       .--\/--.
  B3 --|1   16|-- VCC
IA<B --|2   15|-- A3
IA=B --|3   14|-- B2
IA>B --|4   13|-- A2
QA>B --|5   12|-- A1
QA=B --|6   11|-- B1
QA<B --|7   10|-- A0
 GND --|8    9|-- 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

TI 7485 datasheet

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