7485: Difference between revisions

From NESdev Wiki
Jump to navigationJump to search
m (remove pre, use same formatting as other 74xx pinouts)
(reference added (see the function table))
 
Line 21: Line 21:
* QA=B: False if A < B or A > B
* QA=B: False if A < B or A > B
* QA>B: False if A < B, true if A > B
* QA>B: False if A < B, true if A > B
If A = B, then Q = I.
 
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]].
This IC has been proposed as the PRG ROM decoder for [[NROM-368]].
== References ==
* [http://www.ti.com/lit/ds/sdls123/sdls123.pdf TI 7485 datasheet]


[[Category:7400 series|085]]
[[Category:7400 series|085]]

Latest revision as of 10:33, 28 October 2018

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