7 Jan
2005
7 Jan
'05
2:41 a.m.
OK, this might sound like a stupid question, but being somewhat ignorant of
RTL logic in comparison to TTL and other designs, what, if anything, can be
substituted for RTL logic chips?
For example, if I wanted to build one of Don's devices and I wasn't
concerned with using "vintage" chips, could I do it "plug-and-play"
using
current TTL?
Rich
-----Original Message-----
From: cctalk-bounces(a)classiccmp.org
[mailto:cctalk-bounces@classiccmp.org]On Behalf Of Michael Holley
Sent: Friday, January 07, 2005 12:08 AM
To: cctalk(a)classiccmp.org
Subject: RTL Logic
I have acquired some Don Lancaster designs that use RTL logic and I am
looking for spare parts. The MC789 hex inverter is used in all of them and I
have 2 chips. Does anyone have a reasonable source for the MC789, I can get
all I want for $20 a chip.
I also have 2 MC799 buffers that are use in the Microlab. I have found two
each of these (MC725, MC778, MC785, MC792, MC853, MC855) that I will part
with.
SWTPC Digital Logic Microlab
http://www.swtpc.com/mholley/PopularElectronics/Apr1970/PE_Apr1970.htm
Early SWTPC keyboard
http://www.swtpc.com/mholley/PopularElectronics/Apr1974/PE_Apr1974.htm
I think that Don Lancaster's TIC TAC TOE machine from 1971 is a very clever
design. It uses 5 ICs and 60 diodes to play the game. I may build one.
http://www.swtpc.com/mholley/RadioElectronics/Dec1971/RE_Dec1971.htm
Michael Holley
www.swtpc.com/mholley
7 Jan
7 Jan
5:56 a.m.
The MC789 is a hex inverter, a 7404 or 7406 could be used but the pin-out is
different :(
There are two simple solutions: an adapter or a foil change.
With an adapter you are able to keep looking for the right part. With a
foil change it looks better.
Randy
----- Original Message -----
From: "Cini, Richard" <RCini(a)congressfinancial.com>
To: "'General Discussion: On-Topic and Off-Topic Posts'"
<cctalk(a)classiccmp.org>
Sent: Friday, January 07, 2005 7:41 AM
Subject: RE: RTL Logic
OK, this might sound like a stupid question, but being
somewhat ignorant
of
RTL logic in comparison to TTL and other designs, what, if anything, can
be
substituted for RTL logic chips?
For example, if I wanted to build one of Don's devices and I wasn't
concerned with using "vintage" chips, could I do it "plug-and-play"
using
current TTL?
Rich
-----Original Message-----
From: cctalk-bounces(a)classiccmp.org
[mailto:cctalk-bounces@classiccmp.org]On Behalf Of Michael Holley
Sent: Friday, January 07, 2005 12:08 AM
To: cctalk(a)classiccmp.org
Subject: RTL Logic
I have acquired some Don Lancaster designs that use RTL logic and I am
looking for spare parts. The MC789 hex inverter is used in all of them and
I
have 2 chips. Does anyone have a reasonable source for the MC789, I can
get
all I want for $20 a chip.
I also have 2 MC799 buffers that are use in the Microlab. I have found two
each of these (MC725, MC778, MC785, MC792, MC853, MC855) that I will part
with.
SWTPC Digital Logic Microlab
http://www.swtpc.com/mholley/PopularElectronics/Apr1970/PE_Apr1970.htm
Early SWTPC keyboard
http://www.swtpc.com/mholley/PopularElectronics/Apr1974/PE_Apr1974.htm
I think that Don Lancaster's TIC TAC TOE machine from 1971 is a very
clever
design. It uses 5 ICs and 60 diodes to play the game. I may build one.
http://www.swtpc.com/mholley/RadioElectronics/Dec1971/RE_Dec1971.htm
Michael Holley
www.swtpc.com/mholley
8:19 a.m.
On Fri, 7 Jan 2005, Cini, Richard wrote:
OK, this might sound like a stupid question, but being
somewhat ignorant of
RTL logic in comparison to TTL and other designs, what, if anything, can be
substituted for RTL logic chips?
For example, if I wanted to build one of Don's devices and I wasn't
concerned with using "vintage" chips, could I do it "plug-and-play"
using
current TTL?
It's an interesting idea. There are different types of RTL,
wanting supply voltages not +5VDC sometimes. TTL may not like
running at 6V, the magic smoke may leave. I'd use 74HC instead.
It will live at 6V.
I doubt any of them would have the same pinouts, first off. There
would be problems mapping functions (flipflops with right in/out
combinations, etc) but a few hours with a couple of databooks
would probably work that out.
You'd probably end up with little daughter boards per-chip, not
much fun to consider, but if you only need one or two it's
probably fine. It could be as little as pin swaps and a resistor
or two, or as much as two chips plus glue passives.
None of the RTL chips have much complexity, so that's a plus.
tomj
Rich
-----Original Message-----
From: cctalk-bounces(a)classiccmp.org
[mailto:cctalk-bounces@classiccmp.org]On Behalf Of Michael Holley
Sent: Friday, January 07, 2005 12:08 AM
To: cctalk(a)classiccmp.org
Subject: RTL Logic
I have acquired some Don Lancaster designs that use RTL logic and I am
looking for spare parts. The MC789 hex inverter is used in all of them and I
have 2 chips. Does anyone have a reasonable source for the MC789, I can get
all I want for $20 a chip.
I also have 2 MC799 buffers that are use in the Microlab. I have found two
each of these (MC725, MC778, MC785, MC792, MC853, MC855) that I will part
with.
SWTPC Digital Logic Microlab
http://www.swtpc.com/mholley/PopularElectronics/Apr1970/PE_Apr1970.htm
Early SWTPC keyboard
http://www.swtpc.com/mholley/PopularElectronics/Apr1974/PE_Apr1974.htm
I think that Don Lancaster's TIC TAC TOE machine from 1971 is a very clever
design. It uses 5 ICs and 60 diodes to play the game. I may build one.
http://www.swtpc.com/mholley/RadioElectronics/Dec1971/RE_Dec1971.htm
Michael Holley
www.swtpc.com/mholley
8:26 a.m.
The +6v is not used for the chips. The +6v goes through discrete
transistors to drive lamps.
Randy
----- Original Message -----
From: "Tom Jennings" <tomj(a)wps.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk(a)classiccmp.org>
Sent: Friday, January 07, 2005 1:19 PM
Subject: RE: RTL Logic
On Fri, 7 Jan 2005, Cini, Richard wrote:
OK, this might sound like a stupid question, but
being somewhat ignorant
of
RTL logic in comparison to TTL and other designs, what, if anything, can
be
substituted for RTL logic chips?
For example, if I wanted to build one of Don's devices and I wasn't
concerned with using "vintage" chips, could I do it "plug-and-play"
using
current TTL?
It's an interesting idea. There are different types of RTL,
wanting supply voltages not +5VDC sometimes. TTL may not like
running at 6V, the magic smoke may leave. I'd use 74HC instead.
It will live at 6V.
I doubt any of them would have the same pinouts, first off. There
would be problems mapping functions (flipflops with right in/out
combinations, etc) but a few hours with a couple of databooks
would probably work that out.
You'd probably end up with little daughter boards per-chip, not
much fun to consider, but if you only need one or two it's
probably fine. It could be as little as pin swaps and a resistor
or two, or as much as two chips plus glue passives.
None of the RTL chips have much complexity, so that's a plus.
tomj
Rich
-----Original Message-----
From: cctalk-bounces(a)classiccmp.org
[mailto:cctalk-bounces@classiccmp.org]On Behalf Of Michael Holley
Sent: Friday, January 07, 2005 12:08 AM
To: cctalk(a)classiccmp.org
Subject: RTL Logic
I have acquired some Don Lancaster designs that use RTL logic and I am
looking for spare parts. The MC789 hex inverter is used in all of them
and I
have 2 chips. Does anyone have a reasonable source for the MC789, I can
get
all I want for $20 a chip.
I also have 2 MC799 buffers that are use in the Microlab. I have found
two
each of these (MC725, MC778, MC785, MC792, MC853, MC855) that I will part
with.
SWTPC Digital Logic Microlab
http://www.swtpc.com/mholley/PopularElectronics/Apr1970/PE_Apr1970.htm
Early SWTPC keyboard
http://www.swtpc.com/mholley/PopularElectronics/Apr1974/PE_Apr1974.htm
I think that Don Lancaster's TIC TAC TOE machine from 1971 is a very
clever
design. It uses 5 ICs and 60 diodes to play the game. I may build one.
http://www.swtpc.com/mholley/RadioElectronics/Dec1971/RE_Dec1971.htm
Michael Holley
www.swtpc.com/mholley
12:55 p.m.
OK, this might sound like a stupid question, but being somewhat ignorant of
RTL logic in comparison to TTL and other designs, what, if anything, can be
substituted for RTL logic chips?
For example, if I wanted to build one of Don's devices and I wasn't
concerned with using "vintage" chips, could I do it "plug-and-play"
using
current TTL?
It is difficult to mix RTL and TTL in the same circuit, the supply
voltage and logic levels are different.
RTL chips are slower, and have different switching characteristics to
TTL. If the devices are used as plain digital devices, and if the timing
delays are not critical, then you should be able to built one of those
circuits using entirley TTL devices. But if they use gates as oscillators
or monostables (read : If there are RC networks about), then you will
almost certainly need to make some changes.
The other thing to watch out for is that many older logic families
(certainly DTL, I suspect RTL too) had passive (resistive) pull-ups on the
outputs, and could be wire-ANDed without problems. TTL, of course cannot,
unless you use open-collector devices with an external pull-up resistor.
The bottom line : You can almost certainly make a functionally-identical
device with TTL and the changes will not be that major, but there could
well be changes, It may not be just a matter of replacing a NAND gate
with a NAND gate, etc.
-tony
4:20 p.m.
On Fri, 7 Jan 2005 23:55:00 +0000 (GMT)
ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
Doesn't 4000-series CMOS logic operate pretty well at non-5 volt levels
if powered to such levels? I haven't used any in years, but all the
'building block' logic components are available, i.e. the 4049 and such.
A company I worked for made a muscle stim device out of a single 4000
series 'hex converter' using feedback to make multivibrators, crude
comparators, drivers, etc. out of the gates. It wasn't powered at 5
volts, the whole thing ran from a 9 volt battery. The logic thresholds
for 4000 CMOS are 1/3 and 2/3 of VCC, for whatever VCC you supply, if I
recall.
OK, this might sound like a stupid question, but being somewhat
ignorant of RTL logic in comparison to TTL and other designs, what,
if anything, can be substituted for RTL logic chips?
For example, if I wanted to build one of Don's devices and I wasn't
concerned with using "vintage" chips, could I do it "plug-and-play"
using current TTL?
It is difficult to mix RTL and TTL in the same circuit, the supply
voltage and logic levels are different.
RTL chips are slower, and have different switching characteristics to
TTL. If the devices are used as plain digital devices, and if the
timing delays are not critical, then you should be able to built one
of those circuits using entirley TTL devices. But if they use gates as
oscillators or monostables (read : If there are RC networks about),
then you will almost certainly need to make some changes.
The other thing to watch out for is that many older logic families
(certainly DTL, I suspect RTL too) had passive (resistive) pull-ups on
the outputs, and could be wire-ANDed without problems. TTL, of course
cannot, unless you use open-collector devices with an external pull-up
resistor.
The bottom line : You can almost certainly make a
functionally-identical device with TTL and the changes will not be
that major, but there could well be changes, It may not be just a
matter of replacing a NAND gate with a NAND gate, etc.
-tony 
4:57 p.m.
Doesn't 4000-series CMOS logic operate pretty well
at non-5 volt
levels if powered to such levels?
Which brings up something I've wondered about for a long time: what
goes wrong with TTL when powered at other than 5V? "It doesn't work",
yes, but _why_? I've got schematics for many of the simpler circuits
in my data book, and I can't see anything there that I wouldn't expect
to work equally well at anywhere from 3 volts or so up to the point at
which either currents get so high that dissipated power cooks something
or insulating layers break down, whichever happens first.
So there's obviously something I don't quite understand going on, and
there are few better places to learn such things than here. :-)
Besides, the data book itself, never mind the parts described in it, is
on topic by now. Heck, I personally used it in the late '70s.
/~\ The ASCII der Mouse
\ / Ribbon Campaign
X Against HTML mouse(a)rodents.montreal.qc.ca
/ \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
5:54 p.m.
The specific circuits in question are a mix of TTL & RTL and are simple
gates easily substituted with all TTL.
Randy
www.s100-manuals.com
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <cctalk(a)classiccmp.org>
Sent: Friday, January 07, 2005 5:55 PM
Subject: Re: RTL Logic
OK, this might sound like a stupid question, but being somewhat ignorant
of
RTL logic in comparison to TTL and other designs, what, if anything, can
be
substituted for RTL logic chips?
For example, if I wanted to build one of Don's devices and I wasn't
concerned with using "vintage" chips, could I do it "plug-and-play"
using
current TTL?
It is difficult to mix RTL and TTL in the same circuit, the supply
voltage and logic levels are different.
RTL chips are slower, and have different switching characteristics to
TTL. If the devices are used as plain digital devices, and if the timing
delays are not critical, then you should be able to built one of those
circuits using entirley TTL devices. But if they use gates as oscillators
or monostables (read : If there are RC networks about), then you will
almost certainly need to make some changes.
The other thing to watch out for is that many older logic families
(certainly DTL, I suspect RTL too) had passive (resistive) pull-ups on the
outputs, and could be wire-ANDed without problems. TTL, of course cannot,
unless you use open-collector devices with an external pull-up resistor.
The bottom line : You can almost certainly make a functionally-identical
device with TTL and the changes will not be that major, but there could
well be changes, It may not be just a matter of replacing a NAND gate
with a NAND gate, etc.
-tony
7170
days inactive
7170
days old
8 comments
6 participants
participants (6)
-
ard＠p850ug1.demon.co.uk -
chenmel＠earthlink.net -
mouse＠Rodents.Montreal.QC.CA -
randy＠s100-manuals.com -
RCini＠congressfinancial.com -
tomj＠wps.com