7 Jan
2005
7 Jan
'05
5:24 a.m.
It's funny to have a good discussion based on projects published over 30
years ago.
For the OP, modifying the original project to use currently available
devices, especially if you use devices that were contemporaneous seems OK to
me. I would not be surprised if people used 7404's or 7406's to build some
of these projects when they first came out.
I would be curious to know the reasoning of using RTL chips when TTL chips
were available considering they are driven out of spec, maybe Don was just
more comfortable with them or that is what he had laying around.
Randy
----- Original Message -----
From: "Dwight K. Elvey" <dwight.elvey(a)amd.com>
To: <cctalk(a)classiccmp.org>
Sent: Friday, January 07, 2005 12:52 PM
Subject: RE: RTL Logic
Hi
Most of these were designed such that a single
output pullup resistor didn't use all of the
sink of an output transistor. This means that
two outputs tied together and would not draw too much
current.
DTL does the same thing and allows the wired AND.
As I recall, with RTL, you only needed to apply
power to one device if they were inverters
since there was no other active logic,
like flops.
Dwight
From: "Steve Thatcher"
<melamy(a)earthlink.net>
I don't see how doing a wired-and is possible when RTL includes a pullup
resistor on each output. You would get to a point where an individual
output
transistor would not be capable of sinking all the "low" current.
>
>You can get a basic idea of the logic families here...
>
>http://www.asic-world.com/digital/gates5.html
>
>best regards, Steve Thatcher
>
>
>-----Original Message-----
>From: "Dwight K. Elvey" <dwight.elvey(a)amd.com>
>Sent: Jan 7, 2005 12:22 PM
>To: cctalk(a)classiccmp.org
>Subject: RE: RTL Logic
>
>Oops!
> I forgot one thing. You can put several RTL outputs in
>parallel as a wired AND. You can't do that with the
>general CMOS or TTL. You'd need to look out for this.
> Does anyone have a source for DTL parts. There are
>a could I've been looking for.
>Dwight