----------------------Original Message------------------------ One question. Assuming the signal names are conventional, that's the same pinout as the '154 decoder. And yet my (ancient, hardbacked) TI TTL book says that while the 74154 is a logical replacement, it's not a direct replacement (this implies to me a different pinout). One of the pinouts I received had the A inputs in the oposite order (20 = A0 .. 23 = A3). Can somebody please check which is correct. -tony ------------------------------------------------------------------------ Well, you'll probably get another dozen replies from the other helpful folks here, but the pinouts and logic tables are identical and 23=a0, 20=a3. I thought the same when I looked at the 9311, that it sure looked like a 74154 which was used everywhere, and that there must be a pinout or big characteristic difference to make it worth FSC's while (since they also made the '154, and TI, NSC and Motorola, who also made the 9311). But the only difference I can see is that the max propagation delay is less on the 9311; maybe someone else will see something else. mike