7485

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

• TI 7485 datasheet