15 Nov
2014
15 Nov
'14
12:07 a.m.
Decided to take a good shot at putting my only S-100 serial board to use.
Figured the place to start was ID'ing the connector pin-outs so I could set
up a cable and begin the process.
Lacking any docs whatsoever, all I could do was trace out the PCB and try
to ascertain what was what. So here's what I've come up with - can +you+
figure out which pin is which?
Board has two outputs, J1 & J2. They are standard 10-pin DIP headers, using
the standard numbering scheme. We'll look at J1; J2 is essentially the
same, but routes to different pins / chips / transistors.
Pin 1 - Col. of 2N3906 (Base is driven by opt. 2 of 1458 - see Pin 7)
Pin 2 - Pin 28 (DB3) of both 1014 & 1015 UARTs
Pin 3 - 1K pull-up to Vcc (12V? Same Vcc as 1458s)
Pin 4 - 150R -> 47R -> Pin 6 w/ XNOR input 1A at 150/47 junction
Pin 5 - n/c
Pin 6 - 47R -> 150R -> Pin 4 w/ XNOR input 1A at 150/47 junction
Pin 7 - 1K2 -> opt. 2 of 1458 (see Pin 1)
Pin 8 - GND
Pin 9 - 1458 opt. 1
Pin 10 - GND
So we have what looks like three (3) each Inputs & Outputs, plus a Vcc and
GNDs:
Inputs - Pin 2, 4, 6
Outputs - Pin 1, 7, 9
Vcc - Pin 3
Gnd - Pin 8, 10
So.. what do +you+ make of it? =)
15 Nov
15 Nov
3:10 p.m.
On Fri, 14 Nov 2014, drlegendre . wrote:
Decided to take a good shot at putting my only S-100
serial board to
use. Figured the place to start was ID'ing the connector pin-outs so I
could set up a cable and begin the process.
Lacking any docs whatsoever, all I could do was trace out the PCB and
try to ascertain what was what. So here's what I've come up with - can
+you+ figure out which pin is which?
Board has two outputs, J1 & J2. They are standard 10-pin DIP headers,
using the standard numbering scheme. We'll look at J1; J2 is essentially
the same, but routes to different pins / chips / transistors.
Pin 1 - Col. of 2N3906 (Base is driven by opt. 2 of 1458 - see Pin 7)
Pin 2 - Pin 28 (DB3) of both 1014 & 1015 UARTs
Pin 3 - 1K pull-up to Vcc (12V? Same Vcc as 1458s)
Pin 4 - 150R -> 47R -> Pin 6 w/ XNOR input 1A at 150/47 junction
Pin 5 - n/c
Pin 6 - 47R -> 150R -> Pin 4 w/ XNOR input 1A at 150/47 junction
Pin 7 - 1K2 -> opt. 2 of 1458 (see Pin 1)
Pin 8 - GND
Pin 9 - 1458 opt. 1
Pin 10 - GND
So we have what looks like three (3) each Inputs & Outputs, plus a Vcc
and GNDs:
Inputs - Pin 2, 4, 6
Outputs - Pin 1, 7, 9
Vcc - Pin 3
Gnd - Pin 8, 10
So.. what do +you+ make of it? =)
Standard numbering scheme? Surely you jest? ;)
Do you mean something like this?
2 4 6 8 10
. . . . .
. . . . .
1 3 5 7 9
It sounds like you've just about got it figured out though. If you have
the datasheet for the 1458 (aren't there 1459s on the board too?) then you
can follow the signals through the level converters back to the UART, and
its datasheet should then tell you exactly which signals are which.
It makes sense that pin 10 would be an extra ground too, since it is quite
possible they originally used a 9-conductor ribbon cable and wouldn't have
connected that pin. You may also find than the signals come out on the
correct pins of a DE9 connected to a 10-pin IDS connector with some
9-conductor ribbon cable.
7:49 p.m.
Howdy,
On Sat, Nov 15, 2014 at 9:10 AM, Tothwolf <tothwolf at concentric.net> wrote:
No joke, you got it right. That's the standard scheme for IDS (I said DIP,
which is the wrong term I think) headers.. across-and-back, as you wrote
it.
Standard numbering scheme? Surely you jest? ;)
Do you mean something like this?
2 4 6 8 10
. . . . .
. . . . .
1 3 5 7 9
It sounds like you've just about got it figured out though. If you have
the datasheet for the 1458 (aren't there 1459s on the board too?) then you
can follow the signals through the level converters back to the UART, and
its datasheet should then tell you exactly which signals are which.
Don't see any 1459s on there, just the pair of 1458s up near the IDS I/O
headers
But yes, you have a point.. I could probably have continued, tracing back
from the 1458 inputs, through the various logic gates,
to the 1014 / 1015
UARTs. But I stopped where I did as it was already pretty
tedious and I
figured I had enough info for you in-the-know types to figure it out at a
glance.. ;-)
That, and I am confused by a couple of my findings, particularly the Pin 4
- Pin 6 relationship. Why are these pins essentially common to each other,
and to the XNOR inputs? One pin has a 47R in series to the XNOR gate, the
other has a 150R in series to that same gate. It's as if the line with the
150R could be asserted 'high' by some line and then the line with the 47R
could re-assert it 'low' - but not all the way to zero, more like to 1/3 of
voltage. See, that makes no sense to me,.
Ditto for the Pin 1 / Pin 7 relationship. Both of these pins are
essentially outputs from the same op-amp output - one is basically a
direct-out from the op-amp #2, the other is via the collector of a PNP
(3906) transistor - the base of which is also tied to op-amp output #2.
This is the stuff that's really confusing me.. is the 3906 acting as an
inverter? If so, why?
To be clear, J1 (10-pin I/O header) has two pins (4 & 6) both tied to the
selfsame +input+ point, and two pins (1 & 7) tied to the selfsame +output+
point. J2 is identical, but it uses a different op-amp and a different XNOR
input. Otherwise, J1 and J2 are carbon-copies of each other, electronically
speaking.
It makes sense that pin 10 would be an extra ground too, since it is quite
possible they originally used a 9-conductor ribbon cable and wouldn't have
connected that pin. You may also find than the signals come out on the
correct pins of a DE9 connected to a 10-pin IDS connector with some
9-conductor ribbon cable.
Or to a 25-pin version of the same. Sure wish I had one! But I tossed /
gave all that away years ago, I think.. =/
7:52 p.m.
Oh, and to add to my confusion.. I've read that the early Altair serial
boards used a 20mA current-loop transmission standard.. which as far as I
know, is +not+ standard RS-232 stuff. So should I actually expect this
board to be a standard RS-232 device, or is it something else.?
On Sat, Nov 15, 2014 at 1:49 PM, drlegendre . <drlegendre at gmail.com> wrote:
Howdy,
On Sat, Nov 15, 2014 at 9:10 AM, Tothwolf <tothwolf at concentric.net> wrote:
No joke, you got it right. That's the standard scheme for IDS (I said DIP,
which is the wrong term I think) headers.. across-and-back, as you wrote
it.
Standard numbering scheme? Surely you jest? ;)
Do you mean something like this?
2 4 6 8 10
. . . . .
. . . . .
1 3 5 7 9
It sounds like you've just about got it figured out though. If you have
the datasheet for the 1458 (aren't there 1459s on the board too?) then you
can follow the signals through the level converters back to the UART, and
its datasheet should then tell you exactly which signals are which.
Don't see any 1459s on there, just the pair of 1458s up near the IDS I/O
headers
But yes, you have a point.. I could probably have continued, tracing back
from the 1458 inputs, through the various logic gates, to the 1014 / 1015
UARTs. But I stopped where I did as it was already pretty tedious and I
figured I had enough info for you in-the-know types to figure it out at a
glance.. ;-)
That, and I am confused by a couple of my findings, particularly the Pin 4
- Pin 6 relationship. Why are these pins essentially common to each other,
and to the XNOR inputs? One pin has a 47R in series to the XNOR gate, the
other has a 150R in series to that same gate. It's as if the line with the
150R could be asserted 'high' by some line and then the line with the 47R
could re-assert it 'low' - but not all the way to zero, more like to 1/3 of
voltage. See, that makes no sense to me,.
Ditto for the Pin 1 / Pin 7 relationship. Both of these pins are
essentially outputs from the same op-amp output - one is basically a
direct-out from the op-amp #2, the other is via the collector of a PNP
(3906) transistor - the base of which is also tied to op-amp output #2.
This is the stuff that's really confusing me.. is the 3906 acting as an
inverter? If so, why?
To be clear, J1 (10-pin I/O header) has two pins (4 & 6) both tied to the
selfsame +input+ point, and two pins (1 & 7) tied to the selfsame +output+
point. J2 is identical, but it uses a different op-amp and a different XNOR
input. Otherwise, J1 and J2 are carbon-copies of each other, electronically
speaking.
It makes sense that pin 10 would be an extra ground too, since it is
quite possible they originally used a 9-conductor ribbon cable and wouldn't
have connected that pin. You may also find than the signals come out on the
correct pins of a DE9 connected to a 10-pin IDS connector with some
9-conductor ribbon cable.
Or to a 25-pin version of the same. Sure wish I had one! But I tossed /
gave all that away years ago, I think.. =/
9:02 p.m.
On 11/15/2014 11:52 AM, drlegendre . wrote:
Oh, and to add to my confusion.. I've read that
the early Altair serial
boards used a 20mA current-loop transmission standard.. which as far as I
know, is +not+ standard RS-232 stuff. So should I actually expect this
board to be a standard RS-232 device, or is it something else.?
I have an Altair SIO-1 board. Yes, it can drive a TTY, but that's just
an option. I used it in RS232C mode. One serial port on an S100
board--waste of space.
If memory serves, the only terminal MITS originally sold for the Altair
was an ASR-33 TTY, so the current-loop interface was important.
--Chuck
9:18 p.m.
On 11/15/2014 01:52 PM, drlegendre . wrote:
Oh, and to add to my confusion.. I've read that
the early Altair serial
boards used a 20mA current-loop transmission standard.. which as far as I
know, is +not+ standard RS-232 stuff. So should I actually expect this
board to be a standard RS-232 device, or is it something else.?
Are you even sure that it's intended as a terminal board, rather than for
some other peripheral that happens to be serial in nature?
10:47 p.m.
Jules & All,
On Sat, Nov 15, 2014 at 3:18 PM, Jules Richardson <
jules.richardson99 at gmail.com> wrote:
Are you even sure that it's intended as a terminal board, rather than for
some other peripheral that happens to be serial in nature?
Now why did you have to go and ask +that+? ;-)
No, I guess I don't know for sure, but here's what I do know - the last
owner did have +some+ way of talking to the system (in its previous
configuration), and this is the +only+ board in the lot that even comes
close to resembling a communications card. The other boards are a Z-80
CPU, a 64K dynamic RAM and a dual floppy-disk controller.
The Z-80 CPU board does have both serial & parallel I/O edge-connectors on
it, but they look to have had little to zero use.. maybe one or two
connection cycles at most, perhaps just one cycle for factory QA testing.
Also, and this was dumb of me, I recall the serial board having a cable
+soldered+ directly to it. It only had 3 wires which terminated in a 25-pin
sub-D male connector, with only 3 pins installed. It struck me (like much
of the system) to have been a careless bodge or hack of some sort, so I
must have de-soldered it. Now, I can't even locate that cable, or tell
where it was previously attached.
11:04 p.m.
FYI - I put up a couple photos of the board at:
http://nerp.net/~legendre/altair/mct_serial_01.jpg
http://nerp.net/~legendre/altair/mct_serial_02.jpg
On Sat, Nov 15, 2014 at 4:47 PM, drlegendre . <drlegendre at gmail.com> wrote:
Jules & All,
On Sat, Nov 15, 2014 at 3:18 PM, Jules Richardson <
jules.richardson99 at gmail.com> wrote:
Are you even sure that it's intended as a terminal board, rather than for
some other peripheral that happens to be serial in nature?
Now why did you have to go and ask +that+? ;-)
No, I guess I don't know for sure, but here's what I do know - the last
owner did have +some+ way of talking to the system (in its previous
configuration), and this is the +only+ board in the lot that even comes
close to resembling a communications card. The other boards are a Z-80
CPU, a 64K dynamic RAM and a dual floppy-disk controller.
The Z-80 CPU board does have both serial & parallel I/O edge-connectors on
it, but they look to have had little to zero use.. maybe one or two
connection cycles at most, perhaps just one cycle for factory QA testing.
Also, and this was dumb of me, I recall the serial board having a cable
+soldered+ directly to it. It only had 3 wires which terminated in a 25-pin
sub-D male connector, with only 3 pins installed. It struck me (like much
of the system) to have been a careless bodge or hack of some sort, so I
must have de-soldered it. Now, I can't even locate that cable, or tell
where it was previously attached.
11:37 p.m.
On Sat, 15 Nov 2014, drlegendre . wrote:
FYI - I put up a couple photos of the board at:
http://nerp.net/~legendre/altair/mct_serial_01.jpg
http://nerp.net/~legendre/altair/mct_serial_02.jpg
What happened with the charred area between the uarts and the edge
connector (hopefully not conductive)? Did that pair of tantalum capacitors
burn up? Nichicon PW series low-esr aluminum electrolytics make for an
excellent radial tantalum replacement.
16 Nov
16 Nov
2:42 a.m.
Howdy,
On Sat, Nov 15, 2014 at 5:37 PM, Tothwolf <tothwolf at concentric.net> wrote:
Ah, that info must have been part of a different discussion.. and it might
also be a clue, since the board was (apparently?) operating in +some+ form
prior to the repair..
Those charred areas locate the 12V zener diodes & dropping resistors that
form the +/- 12V supplies for the board. As received, the board was already
like this, and the offending components had been simply cut away - this all
happened long before my time with it.
Now obviously, I didn't initially know what was supposed to be there. But I
started tracing the board and found that one set of traces went to the -12V
supply input for the original 1013 UARTs as well as the GND / -Vcc
terminals of the 1458 op-amps. Now, the present UARTs no longer require a
-12V supply - that need was eliminated with the 1014/1015, so they would
have been fine without the zener reg.. But the op-amps most certainly do
require a bipolar supply (if they're going to do real RS-232 conversion,
right?).
So that tells me that whatever was going on previously wasn't using the
board as originally designed.. because the never bothered to replace the
+/- regs once they killed them. I went ahead and fixed them, this time with
5W zeners and 1.2W resistors. Now I'm thinking.. I need to see if there's a
hack anywhere on that board to supply single-supply 8V or 5V power to the
op-amps.. but I think they need more than 5V, don't they? (time to look at
the datasheet)
What happened with the charred area between the
uarts and the edge
connector (hopefully not conductive)? Did that pair of tantalum
capacitors
burn up? Nichicon PW series low-esr aluminum electrolytics make for an
excellent radial tantalum replacement.
4:18 a.m.
Quick update - I made an error.
Pin 3 (both i/o headers) isn't tied to the 1458 Vcc+ - they're tied to the
1458 Vcc-. So, they have a 1K pull-down to -12V rather than a pull-up to
+12V.
So why is there a pin (3) on each header that's essentially a -12V @ 12mA
current source?
On Sat, Nov 15, 2014 at 8:42 PM, drlegendre . <drlegendre at gmail.com> wrote:
Howdy,
On Sat, Nov 15, 2014 at 5:37 PM, Tothwolf <tothwolf at concentric.net> wrote:
Ah, that info must have been part of a different discussion.. and it might
also be a clue, since the board was (apparently?) operating in +some+ form
prior to the repair..
Those charred areas locate the 12V zener diodes & dropping resistors that
form the +/- 12V supplies for the board. As received, the board was already
like this, and the offending components had been simply cut away - this all
happened long before my time with it.
Now obviously, I didn't initially know what was supposed to be there. But
I started tracing the board and found that one set of traces went to the
-12V supply input for the original 1013 UARTs as well as the GND / -Vcc
terminals of the 1458 op-amps. Now, the present UARTs no longer require a
-12V supply - that need was eliminated with the 1014/1015, so they would
have been fine without the zener reg.. But the op-amps most certainly do
require a bipolar supply (if they're going to do real RS-232 conversion,
right?).
So that tells me that whatever was going on previously wasn't using the
board as originally designed.. because the never bothered to replace the
+/- regs once they killed them. I went ahead and fixed them, this time with
5W zeners and 1.2W resistors. Now I'm thinking.. I need to see if there's a
hack anywhere on that board to supply single-supply 8V or 5V power to the
op-amps.. but I think they need more than 5V, don't they? (time to look at
the datasheet)
What happened with the charred area between the
uarts and the edge
connector (hopefully not conductive)? Did that pair of tantalum
capacitors
burn up? Nichicon PW series low-esr aluminum electrolytics make for an
excellent radial tantalum replacement.
5:02 a.m.
Ok, I think I've made some progress..
Header pins 1 & 7 are both common to opt #2 of the op-amp. The inputs of
op-amp #2 are as follows - the +IN seems to be tied to a voltage ref, but
the -IN is tied to the SEROUT (serial output) of the UART.
Sooo.. header pins 1 & 7 are both serial outputs, though one is a 'direct'
out (via a 1K2) and the other is via the collector of a 3906 PNP. So if you
view this with the pin 4 & 6 situation in mind, it does seem that this
board provides both 'plain' (RS-232?) outputs as well as current-loop
outputs, PLUS 'plain' and current-loop inputs - on the same header.
Am I getting that right??
Also, I found more interesting info.. Header pin 9 is connected to opt #1
of the op-amp. The +IN of #1 seems to again be tied to a voltage ref, but
the -IN is tied to the DAV line (Data Available) of the UART. Apparently,
DAV goes high when a full character has been received and is ready to be
read-out of the UART buffer. So this must be the... I don't know.. a line
that goes 'hi' when the UART can receive no more bits and must wait till
the current char is read-out. So this must be something like the DSR / DTR
line? Letting the other end know that it can't send more bits till the UART
buffer has been read?
On Sat, Nov 15, 2014 at 10:18 PM, drlegendre . <drlegendre at gmail.com> wrote:
Quick update - I made an error.
Pin 3 (both i/o headers) isn't tied to the 1458 Vcc+ - they're tied to the
1458 Vcc-. So, they have a 1K pull-down to -12V rather than a pull-up to
+12V.
So why is there a pin (3) on each header that's essentially a -12V @ 12mA
current source?
On Sat, Nov 15, 2014 at 8:42 PM, drlegendre . <drlegendre at gmail.com>
wrote:
Howdy,
On Sat, Nov 15, 2014 at 5:37 PM, Tothwolf <tothwolf at concentric.net>
wrote:
Ah, that info must have been part of a different discussion.. and it
might also be a clue, since the board was (apparently?) operating in +some+
form prior to the repair..
Those charred areas locate the 12V zener diodes & dropping resistors that
form the +/- 12V supplies for the board. As received, the board was already
like this, and the offending components had been simply cut away - this all
happened long before my time with it.
Now obviously, I didn't initially know what was supposed to be there. But
I started tracing the board and found that one set of traces went to the
-12V supply input for the original 1013 UARTs as well as the GND / -Vcc
terminals of the 1458 op-amps. Now, the present UARTs no longer require a
-12V supply - that need was eliminated with the 1014/1015, so they would
have been fine without the zener reg.. But the op-amps most certainly do
require a bipolar supply (if they're going to do real RS-232 conversion,
right?).
So that tells me that whatever was going on previously wasn't using the
board as originally designed.. because the never bothered to replace the
+/- regs once they killed them. I went ahead and fixed them, this time with
5W zeners and 1.2W resistors. Now I'm thinking.. I need to see if there's a
hack anywhere on that board to supply single-supply 8V or 5V power to the
op-amps.. but I think they need more than 5V, don't they? (time to look at
the datasheet)
What happened with the charred area between the
uarts and the edge
connector (hopefully not conductive)? Did that pair of tantalum
capacitors
burn up? Nichicon PW series low-esr aluminum electrolytics make for an
excellent radial tantalum replacement.
6:06 a.m.
Ok, I think I've made some progress..
Header pins 1 & 7 are both common to opt #2 of the op-amp. The inputs of
op-amp #2 are as follows - the +IN seems to be tied to a voltage ref, but
the -IN is tied to the SEROUT (serial output) of the UART.
Sooo.. header pins 1 & 7 are both serial outputs, though one is a 'direct'
out (via a 1K2) and the other is via the collector of a 3906 PNP. So if you
view this with the pin 4 & 6 situation in mind, it does seem that this
board provides both 'plain' (RS-232?) outputs as well as current-loop
outputs, PLUS 'plain' and current-loop inputs - on the same header.
I think so. The current loop connection is the collector of a PNP transistor (2N3906)
which
suggests that's the positive side of the loop (emitter to a +ve voltage). So my next
guess is that that
pin with the 1k resistor to -12V is the -ve side of the loop. If the transistor emitter
goes to +12V or something
like that you have a 20-odd mA loop which seems about right.
I still want to know more about the input circuitry...
Am I getting that right??
Also, I found more interesting info.. Header pin 9 is connected to opt #1
of the op-amp. The +IN of #1 seems to again be tied to a voltage ref, but
the -IN is tied to the DAV line (Data Available) of the UART. Apparently,
DAV goes high when a full character has been received and is ready to be
read-out of the UART buffer. So this must be the... I don't know.. a line
that goes 'hi' when the UART can receive no more bits and must wait till
the current char is read-out. So this must be something like the DSR / DTR
line? Letting the other end know that it can't send more bits till the UART
buffer has been read?
My guess, again, is that this is related to using the board with an ASR33. It was a
common
modification to such teletypes to add a reader control relay, allowing the computer to
start
and stop the paper tape reader. DEC, HP, Intel all did it (in much the same way) for
their
machines. I am going to guess that this output is to operate such a relay so you can use
the
paper tape reader (e.g. to load software) and not loose characters.
-tony
15 Nov
15 Nov
9:27 p.m.
On Sat, 15 Nov 2014, drlegendre . wrote:
As Tony pointed out, I was thinking 1488/1489, so disregard that.
Those likely wouldn't have worked with this board since it doesn't look to
be purely RS232. Even the generic boards that used the 10 pin IDS to DE9
or DB25 cables varied on their pinouts so there were multiple pinouts for
the cables. With a straight through ribbon cable and an IDC press-on type
DE9 connector, you'd get a pinout such as this:
IDS DE9 RS232
1 1 DCD
2 6 DSR
3 2 RXD
4 7 RTS
5 3 TXD
6 8 CTS
7 4 DTR
8 9 RI
9 5 GND
10 NC
...but some companies would instead use solder cup DE9 / DB25 connectors
and would split or fold the ribbon cable around different ways from 1->9
or 1->5, 9->6, etc for DE9 and the DB25 cables had even more variations.
On Sat, Nov 15, 2014 at 9:10 AM, Tothwolf <tothwolf
at concentric.net> wrote:
I've seen pins labeled all sorts of ways, even though that across-and-back
really does seem to be the correct way to label them.
Standard numbering scheme? Surely you jest? ;)
Do you mean something like this?
2 4 6 8 10
. . . . .
. . . . .
1 3 5 7 9
No joke, you got it right. That's the standard scheme for IDS (I said
DIP, which is the wrong term I think) headers.. across-and-back, as you
wrote it. It sounds like
you've just about got it figured out though. If you have
the datasheet for the 1458 (aren't there 1459s on the board too?) then
you can follow the signals through the level converters back to the
UART, and its datasheet should then tell you exactly which signals are
which.
Don't see any 1459s on there, just the pair of 1458s up near the IDS I/O
headers But yes, you have a point.. I could probably have
continued, tracing
back from the 1458 inputs, through the various logic gates, to the 1014
/ 1015 UARTs. But I stopped where I did as it was already pretty
tedious and I figured I had enough info for you in-the-know types to
figure it out at a glance.. ;-)
I dunno, it is getting beyond what I can figure out without the board in
front of me to trace out too.
That, and I am confused by a couple of my findings,
particularly the Pin
4 - Pin 6 relationship. Why are these pins essentially common to each
other, and to the XNOR inputs? One pin has a 47R in series to the XNOR
gate, the other has a 150R in series to that same gate. It's as if the
line with the 150R could be asserted 'high' by some line and then the
line with the 47R could re-assert it 'low' - but not all the way to
zero, more like to 1/3 of voltage. See, that makes no sense to me,.
Ditto for the Pin 1 / Pin 7 relationship. Both of these pins are
essentially outputs from the same op-amp output - one is basically a
direct-out from the op-amp #2, the other is via the collector of a PNP
(3906) transistor - the base of which is also tied to op-amp output #2.
This is the stuff that's really confusing me.. is the 3906 acting as an
inverter? If so, why?
Many serial interfaces are differential so you wouldn't necessarily expect
a voltage to be at reference to GND for a logical 0. For "real" RS232,
you'd expect a logical low to be below 0 volts, so maybe that's some of
what they are doing here since they aren't using something like 1488/1489
transceivers to do the level conversion?
To be clear, J1 (10-pin I/O header) has two pins (4
& 6) both tied to
the selfsame +input+ point, and two pins (1 & 7) tied to the selfsame
+output+ point. J2 is identical, but it uses a different op-amp and a
different XNOR input. Otherwise, J1 and J2 are carbon-copies of each
other, electronically speaking.
It is looking like the pinout isn't going to be 'standard' RS232 though.
Just pin 5 being NC wouldn't match up with a RS232 pinned DE9 where you
would expect TXD on pin 3.
It makes sense
that pin 10 would be an extra ground too, since it is
quite possible they originally used a 9-conductor ribbon cable and
wouldn't have connected that pin. You may also find than the signals
come out on the correct pins of a DE9 connected to a 10-pin IDS
connector with some 9-conductor ribbon cable.
Or to a 25-pin version of the same. Sure wish I had one! But I tossed /
gave all that away years ago, I think.. =/
7:58 p.m.
It sounds like you've just about got it figured
out though. If you have
the datasheet for the 1458 (aren't there 1459s on the board too?) then you
can follow the signals through the level converters back to the UART, and
its datasheet should then tell you exactly which signals are which.
Are you not thinking of the 1488 and 1489 (commonly used RS232 driver and receiver chips)?
The
1458 is a dual op-amp.
Op amps were often used as level shifters in older RS232 devices. I guess that's what
is happening
here.
-tony
9 p.m.
On Sat, 15 Nov 2014, tony duell wrote:
Yup, I was thinking 1488 and 1489. I guess there wouldn't be a 1489 on
there if they were using a 1458 as a level converter.
It sounds like
you've just about got it figured out though. If you have
the datasheet for the 1458 (aren't there 1459s on the board too?) then
you can follow the signals through the level converters back to the
UART, and its datasheet should then tell you exactly which signals are
which.
Are you not thinking of the 1488 and 1489 (commonly used RS232 driver
and receiver chips)? The 1458 is a dual op-amp.
Op amps were often used as level shifters in older RS232 devices. I
guess that's what is happening here.
7:56 p.m.
Decided to take a good shot at putting my only S-100 serial board to use.
Figured the place to start was ID'ing the connector pin-outs so I could set
up a cable and begin the process.
Lacking any docs whatsoever, all I could do was trace out the PCB and try
to ascertain what was what. So here's what I've come up with - can +you+
figure out which pin is which?
Board has two outputs, J1 & J2. They are standard 10-pin DIP headers, using
the standard numbering scheme. We'll look at J1; J2 is essentially the
same, but routes to different pins / chips / transistors.
Pin 1 - Col. of 2N3906 (Base is driven by opt. 2 of 1458 - see Pin 7)
Pin 2 - Pin 28 (DB3) of both 1014 & 1015 UARTs
Pin 3 - 1K pull-up to Vcc (12V? Same Vcc as 1458s)
Pin 4 - 150R -> 47R -> Pin 6 w/ XNOR input 1A at 150/47 junction
Pin 5 - n/c
Pin 6 - 47R -> 150R -> Pin 4 w/ XNOR input 1A at 150/47 junction
Pin 7 - 1K2 -> opt. 2 of 1458 (see Pin 1)
Pin 8 - GND
Pin 9 - 1458 opt. 1
Pin 10 - GND
So we have what looks like three (3) each Inputs &
Outputs, plus a Vcc and
GNDs:
Inputs - Pin 2, 4, 6
Outputs - Pin 1, 7, 9
Vcc - Pin 3
Gnd - Pin 8, 10
So.. what do +you+ make of it? =)
Well...
First oddity is pin 2? What on earth is that for? Why bring out one data line with no
enables, strobes, etc?
Are you sure about this?
Now, the 1458 is a dual op-amp. It was commonly used in old serial devices as a level
shifter.
My guess is that pin 7 is an RS232-like voltage output, serial data. Pin i is a current
loop output,
same data.
The receive input has me stumped at this point. I would guess it's pins 4 and 6. Again
possibly current loop.
I would trace out all the circuitry in that area. It is probably possible to connect it
for RS232 input, but
no idea how without the complete circuit.
-tony
3769
days inactive
3770
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ard＠p850ug1.demon.co.uk -
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