30 Jun
1999
30 Jun
'99
7:45 a.m.
They're not equivalent, though they share the same pinout and function with
the old National Semiconductor 8097. The 8T97 has greater current
source/sink capability, hence it is faster in some applications and can
drive a pretty stubstantial load. It was very common as a bus driver, which
was it's intended purpose. For normal TTL fanout, either part will work.
Dick
-----Original Message-----
From: Bill Sudbrink <bill(a)chipware.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Wednesday, June 30, 1999 12:56 PM
Subject: 8T97 == 74367 ??
Are these two parts equivalent:
74367AN and N8T97N
Thanks,
Bill
30 Jun
30 Jun
8:26 a.m.
New subject: 8T97 == 74367 ?? (IMSAI front panel)
They're not equivalent, though they share the same
pinout and
function with the old National Semiconductor 8097. The 8T97
has greater current source/sink capability, hence it is faster
in some applications and can drive a pretty stubstantial load.
It was very common as a bus driver, which was it's intended
purpose. For normal TTL fanout, either part will work.
Well, an 8T97 was specified for U24 on the CP-A. U24 had been
socketed and replaced with a 74367. I "undid" the mods around
U24/U25 and populated U24 with an 8T97. A bunch of work, no
change in behavior. Arg!
I also looked at the MPU-A. Sure enough, on the 16 pin header
to the front panel, pins 1-8 are connected to pins D0-D7 on
the 8080, in order (pin1-D0, pin2-D1, etc). They also go a
bunch of other places I have not tried to figure out yet. It's
probably just going to the data lines on the S-100 connector.
Given the C3 instruction, I don't see why everything goes so
wacky when I reverse the header.
I've looked through the docs I got with it and don't have
anything on the MPU-A.
9:03 a.m.
New subject: 8T97 == 74367 ?? (IMSAI front panel)
"Bill Sudbrink" <bill(a)chipware.com> wrote:
I also looked at the MPU-A. Sure enough, on the 16 pin header
to the front panel, pins 1-8 are connected to pins D0-D7 on
the 8080, in order (pin1-D0, pin2-D1, etc). They also go a
bunch of other places I have not tried to figure out yet.
I would think that it also goes to the bus through bus buffers.
The method that is used to jam the instruction sequence in the processor
wouldn't work from the S-100 side because the memory board
would be driving that side. This is why they needed the cable
to get to the uP's data lines.
If you could give me the complete header connections, I'm sure
I could figure out what was the source of the troubles.
Dwight
9:23 a.m.
New subject: 8T97 == 74367 ?? (IMSAI front panel)
I could figure out what was the source of the
troubles.
Dwight
Pin 1 - 8080 D0 (pin 10)
Pin 2 - 8080 D1 (pin 9)
Pin 3 - 8080 D2 (pin 8)
Pin 4 - 8080 D3 (pin 7)
Pin 5 - 8080 D4 (pin 3)
Pin 6 - 8080 D5 (pin 4)
Pin 7 - 8080 D6 (pin 5)
Pin 8 - 8080 D7 (pin 6)
Pin 9 to 16 no connection.
9:55 a.m.
New subject: 8T97 == 74367 ?? (IMSAI front panel)
"Bill Sudbrink" <bill(a)chipware.com> wrote:
Great!
This explains why inverting doesn't work. If you invert the connector,
you connect the signals to 9 thru 16. Since these are not connected,
you get strange behavior.
My first thought is that one end of the cable was poorly crimped
and the ribbon is shifted sideways by one pin ( I've seen this happen ).
The next thought is to simply connect up pins 1 to 16, 2 to 15 ....
8 to 9. Now when you invert the connector, it will reverse the data
and you'll be back in business.
Don't waste time on the 7405 or 8T97, they can't cause the symptoms you
describe. Remember, the first rule of trouble shooting. The
solution has to solve the symptoms. How could a logic part swap
the data lines by a failure? I've never seen it happen. It can
open the lines or short the lines or even leave out one or two.
Dwight
I could figure
out what was the source of the troubles.
Dwight
Pin 1 - 8080 D0 (pin 10)
Pin 2 - 8080 D1 (pin 9)
Pin 3 - 8080 D2 (pin 8)
Pin 4 - 8080 D3 (pin 7)
Pin 5 - 8080 D4 (pin 3)
Pin 6 - 8080 D5 (pin 4)
Pin 7 - 8080 D6 (pin 5)
Pin 8 - 8080 D7 (pin 6)
Pin 9 to 16 no connection. 
9:24 a.m.
New subject: 8T97 == 74367 ?? (IMSAI front panel)
On Wed, 30 Jun 1999, Bill Sudbrink wrote:
I also looked at the MPU-A. Sure enough, on the 16
pin header
to the front panel, pins 1-8 are connected to pins D0-D7 on
the 8080, in order (pin1-D0, pin2-D1, etc). They also go a
bunch of other places I have not tried to figure out yet.
Actually, (working from memory) they should go to the 8212 latch which
then will feed thru to the CPU chip. Might go another place or two as
well, but I'm not in front of a schematic either...
It's
probably just going to the data lines on the S-100 connector.
Not directly... (IIRC)
Given the C3 instruction, I don't see why
everything goes so
wacky when I reverse the header.
Given the 'C3' by itself, there would be no effect, but if you consider
that the entire three byte jump sequence is jammed onto the CPU thru the
cable (inst/hi addr/lo addr) ((watch, I probably got the byte sequence
backwards and will get flamed)) it gets real interesting when the bytes
are assembled and the jump executed...
-jim
---
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29 Jun
29 Jun
11:44 a.m.
New subject: 8T97 == 74367 ?? (IMSAI front panel)
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30 Jun
30 Jun
9:58 a.m.
New subject: 8T97 == 74367 ?? (IMSAI front panel)
James Willing <jimw(a)agora.rdrop.com> wrote:
Given the 'C3' by itself, there would be no effect, but if you consider
that the entire three byte jump sequence is jammed onto the CPU thru the
cable (inst/hi addr/lo addr) ((watch, I probably got the byte sequence
backwards and will get flamed)) it gets real interesting when the bytes
are assembled and the jump executed...
Flame Flame Burn Burn Burn!!!!!
Intel is low byte first then high byte ;)
The way it should be for 8 bit micros from a hardware stand point.
Motorola had extra hardware to solve the wrong way issue.
Dwight
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