[sdiy] TTL Etiquette?

[Magnus Danielson]

From: Metrophage <c0r3dump23 at yahoo.com>
Subject: [sdiy] TTL Etiquette?
Date: Mon, 20 Sep 2004 14:50:12 -0700 (PDT)
Message-ID: <20040920215012.66402.qmail at web50307.mail.yahoo.com>

CJ,

> So this is my entry point to TTL stuff. I used a typical idea for
> deriving a 1 MHZ signal from an available 4 MHZ crystal. I got some LS
> TTL chips for i/o and buffers� my layout looks compact.... but I am
> worried about the unused pins on the buffers and line reciever. I know
> this is probably very basic stuff, but I am worried that I should
> perhaps tie them to ground, or +5v, or just to each other. Maybe some
> unused pins I should orient a certain way, but others I may not need
> to? I figured I'd ask about the experiences of people here while I am
> deciding upon the wiring and component placement before I solder
> anything.
> Any ideas? Thanks!

For real TTL, you can just leave the inputs. For HC and HCT you should have
the decency to hook them to ground or +5V as you see fit. Never bolt an output
to either ground or whatever.

CMOS always require you to bolt unused inputs to something (except maybe to the
electrical wire pointing up in the dark sky that you just got from a fellow
called Franklin). The CMOS HC And HCT variants of TTL should be treated the
same way. The traditional TTL stuff does not require you to do anything, which
is very neat when you want to leave stuff for later. But as you move into CMOS
thats a bad idea (TM).

Don't forget to hook caps over each chip.

Why not just use the 4 MHz clock directly?

Cheers,
Magnus