30 Nov
2015
30 Nov
'15
6:14 p.m.
I have an 11/05 with ASR 33 for I/O. I am using the M9970 console card to
make the connection. I have loaded papertape BASIC into core (16K) and it
boots up from 000 000 to the TTY, I can type in programs, etc.
Question - I'd like to switch over to a VT 50 in 20ma mode. Not sure if
this is possible based on what I read here:
http://www.retrocmp.com/how-tos/interfacing-to-a-pdp-1105/144-interfacing-w…
Anyone successfully connect a VT 50 or 52 to a 11/05 or 11/10 over to the
EIN M7856 for printer and typewriter only, leaving the M9970 for program
i/o to save and load programs?
--
Bill
30 Nov
30 Nov
7:13 p.m.
On Nov 30, 2015 9:14 PM, "william degnan" <billdegnan at gmail.com> wrote:
http://www.retrocmp.com/how-tos/interfacing-to-a-pdp-1105/144-interfacing-w…
To clarify, I meant I don't think you can interface with the vt50 with loop
20ma, so instead I wanted to split the IO between the TTY for program
storage and vt50 using M7856 serial card.
I am guessing this is the way to go, but I have never done this before.
Good plan? Anyone have this kind of set up now?
Bill
I have an 11/05 with ASR 33 for I/O. I am using the M9970 console card
to make the
connection. I have loaded papertape BASIC into core (16K) and
it boots up from 000 000 to the TTY, I can type in programs, etc.
Question - I'd like to switch over to a VT 50 in 20ma mode. Not sure if
this
is possible based on what I read here:
1 Dec
1 Dec
8:55 a.m.
On Nov 30, 2015, at 9:14 PM, william degnan
<billdegnan at gmail.com> wrote:
I have an 11/05 with ASR 33 for I/O. I am using the M9970 console card to
make the connection. I have loaded papertape BASIC into core (16K) and it
boots up from 000 000 to the TTY, I can type in programs, etc.
Question - I'd like to switch over to a VT 50 in 20ma mode. Not sure if
this is possible based on what I read here:
http://www.retrocmp.com/how-tos/interfacing-to-a-pdp-1105/144-interfacing-w…
I'm not sure I understand the question correctly. That article clearly points out the
20 mA wires, and presumably that's where your ASR33 is connected. The VT50 comes
(according to the peripherals handbook) with a standard 20 mA interface, optional RS232
interface. So it sounds like it would be a matter of finding where the 20 mA connector on
the VT50 is, and plugging into that.
Interestingly enough, the VT52 is listed as supporting either kind of interface, but only
one; "specify at time of order".
paul
9:39 a.m.
The VT50 comes (according to the peripherals handbook)
with a standard 20 mA
interface, optional RS232 interface. So it sounds like it would be a matter of finding
where the 20 mA connector on the VT50 is, and plugging into that.
Interestingly enough, the VT52 is listed as supporting either kind of interface, but only
one; "specify at time of order".
I suspect it's the same as the VT55 which I have. That terminal has a little
daughterboard
on the main logic board which contains the interface buffers etc. Mine is 20mA
current loop, I assume the RS232 interface is a simialr daughterboard that replaces it.
9:43 a.m.
On Tue, Dec 1, 2015 at 11:55 AM, Paul Koning <paulkoning at comcast.net> wrote:
I'm not sure I understand the question correctly.
That article clearly points out the 20 mA wires, and presumably that's where your
ASR33 is connected. The VT50 comes (according to the peripherals handbook) with a
standard 20 mA interface, optional RS232 interface. So it sounds like it would be a
matter of finding where the 20 mA connector on the VT50 is, and plugging into that.
Interestingly enough, the VT52 is listed as supporting either kind of interface, but only
one; "specify at time of order".
I don't know that I've taken apart a VT50 or if there are internal
differences, but for the VT52, there's a ~2"x5" (from memory) PCB with
interface circuitry for either EIA or 20mA and a permanently-attached
cable with the appropriate connector on the host end. You take the
bottom of the terminal off, pop the board, pop the other one on and
it's switched.
It would not be difficult to replicate either board, either by hand or
with a fabricated PCB.
-ethan
10:22 a.m.
On Tue, Dec 1, 2015 at 12:43 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
On Tue, Dec 1, 2015 at 11:55 AM, Paul Koning
<paulkoning at comcast.net>
wrote:
Sorry about the wording of my question. Thanks for the replies. I was
only able to get the VT50 to receive, I could not send. So I decided to
research the problem. I found the link above, the author of the page says
in effect 20mA did not work (for him) as desired. So I was wondering if
anyone here has been successful to attach a M9970 to a VT50 or VT52. I
spend more time on it, but I was curious if it was even worth it given the
hardware.
The author writes:
-start quote--
I first tried to connect a PC with the 11/05 over a industrial
RS232-to-20mA converter, but this failed.
A 20mA interface works by one side providing a 20mA current, which drives
receiver and transmitter of the closed loops for Transmit and Receive.
But the 20mA interface of the PDP-11/05 is not a proper one: the receiver
is more like a low impedance voltage sensor, while the transmitter simply
switches voltage at the levels +3.5V to -15 V. At best you call the
PDP-11/05 serial interface a "TTY interface": it is well suited to read
data generated by mechanical switches to GND, and driving solenoids for
transmit data.
-end quote--
--
Bill
I'm not sure I understand the question
correctly. That article clearly
points out the 20 mA wires, and presumably
that's where your ASR33 is
connected. The VT50 comes (according to the peripherals handbook) with a
standard 20 mA interface, optional RS232 interface. So it sounds like it
would be a matter of finding where the 20 mA connector on the VT50 is, and
plugging into that.
Interestingly enough, the VT52 is listed as supporting either kind of
interface,
but only one; "specify at time of order".
I don't know that I've taken apart a VT50 or if there are internal
differences, but for the VT52, there's a ~2"x5" (from memory) PCB with
interface circuitry for either EIA or 20mA and a permanently-attached
cable with the appropriate connector on the host end. You take the
bottom of the terminal off, pop the board, pop the other one on and
it's switched.
It would not be difficult to replicate either board, either by hand or
with a fabricated PCB.
-ethan
10:48 a.m.
10:56 a.m.
On Dec 1, 2015, at 1:22 PM, william degnan
<billdegnan at gmail.com> wrote:
...
Sorry about the wording of my question. Thanks for the replies. I was
only able to get the VT50 to receive, I could not send. So I decided to
research the problem. I found the link above, the author of the page says
in effect 20mA did not work (for him) as desired. So I was wondering if
anyone here has been successful to attach a M9970 to a VT50 or VT52. I
spend more time on it, but I was curious if it was even worth it given the
hardware.
The author writes:
-start quote--
I first tried to connect a PC with the 11/05 over a industrial
RS232-to-20mA converter, but this failed.
A 20mA interface works by one side providing a 20mA current, which drives
receiver and transmitter of the closed loops for Transmit and Receive.
But the 20mA interface of the PDP-11/05 is not a proper one: the receiver
is more like a low impedance voltage sensor, while the transmitter simply
switches voltage at the levels +3.5V to -15 V. At best you call the
PDP-11/05 serial interface a "TTY interface": it is well suited to read
data generated by mechanical switches to GND, and driving solenoids for
transmit data.
-end quote--
Hm. I wonder by what definition it is not "proper". A current loop
transmitter, in an electronic terminal as opposed to a mechanical one, would be a
switching transistor that turns the current on and off. The only issues I can think of
are the voltage rating used, and the polarity. For example, in earlier 60 mA loops (for
the Model 15 Teletype and machines of that era) you might find loop voltages around 100
volts or so, with a big series resistor. The purpose was to reduce the distortion from
the inductance in the loop (in the receive solenoid). In the later 20 mA loops I would
expect lower voltages to be used. But the specification is pretty wide open -- "20
mA" is really about all there is. You can build conforming devices with
optocouplers, switching transistors, solenoids and cam operated switches, etc.
I don't know what "simply switches voltage at the levels +3.5V to -15 V"
means. The voltages at the pins aren't directly relevant, only the voltage difference
between the two transmit pins -- or more precisely, the resulting current in the loop. I
could easily imagine that in the off state both pins are at -15 while in the on state one
goes to +3.5, or something like that, driving through a resistor of a bit under 1000 ohms.
The fact that the "industrial converter" didn't work does not imply that the
VT50 would have troubles. Just the opposite, actually; I would assume that DEC would make
sure that its 20 mA terminals work with its 20 mA host interfaces.
Did you check the voltage and current in the two loops when you hooked it up? I wonder if
you might have the polarity backwards on one of the circuits, assuming that the devices
involved care.
paul
11:58 a.m.
The current loop is actually "proper" .
There are 3 parts to current loop
1) transmitter (switch)
2) receiver (opto coupler in dec stuff)
3) current source
You will have problems if things don't match. An active transmitter has to connect to
a passive receiver.
Passive transmitter to active receiver.
Active means it has a current source,passive no current source.
The 11/05 is active tx active rx. So expects contacts on the keyboard and the selector
magnet in the printer.
Most industrial current loop converters are not this way out of the box.
Joe
On Dec 1, 2015, at 1:56 PM, Paul Koning <paulkoning
at comcast.net> wrote:
On Dec 1, 2015, at 1:22 PM, william degnan
<billdegnan at gmail.com> wrote:
...
Sorry about the wording of my question. Thanks for the replies. I was
only able to get the VT50 to receive, I could not send. So I decided to
research the problem. I found the link above, the author of the page says
in effect 20mA did not work (for him) as desired. So I was wondering if
anyone here has been successful to attach a M9970 to a VT50 or VT52. I
spend more time on it, but I was curious if it was even worth it given the
hardware.
The author writes:
-start quote--
I first tried to connect a PC with the 11/05 over a industrial
RS232-to-20mA converter, but this failed.
A 20mA interface works by one side providing a 20mA current, which drives
receiver and transmitter of the closed loops for Transmit and Receive.
But the 20mA interface of the PDP-11/05 is not a proper one: the receiver
is more like a low impedance voltage sensor, while the transmitter simply
switches voltage at the levels +3.5V to -15 V. At best you call the
PDP-11/05 serial interface a "TTY interface": it is well suited to read
data generated by mechanical switches to GND, and driving solenoids for
transmit data.
-end quote--
Hm. I wonder by what definition it is not "proper". A current loop
transmitter, in an electronic terminal as opposed to a mechanical one, would be a
switching transistor that turns the current on and off. The only issues I can think of
are the voltage rating used, and the polarity. For example, in earlier 60 mA loops (for
the Model 15 Teletype and machines of that era) you might find loop voltages around 100
volts or so, with a big series resistor. The purpose was to reduce the distortion from
the inductance in the loop (in the receive solenoid). In the later 20 mA loops I would
expect lower voltages to be used. But the specification is pretty wide open -- "20
mA" is really about all there is. You can build conforming devices with
optocouplers, switching transistors, solenoids and cam operated switches, etc.
I don't know what "simply switches voltage at the levels +3.5V to -15 V"
means. The voltages at the pins aren't directly relevant, only the voltage difference
between the two transmit pins -- or more precisely, the resulting current in the loop. I
could easily imagine that in the off state both pins are at -15 while in the on state one
goes to +3.5, or something like that, driving through a resistor of a bit under 1000 ohms.
The fact that the "industrial converter" didn't work does not imply that
the VT50 would have troubles. Just the opposite, actually; I would assume that DEC would
make sure that its 20 mA terminals work with its 20 mA host interfaces.
Did you check the voltage and current in the two loops when you hooked it up? I wonder
if you might have the polarity backwards on one of the circuits, assuming that the devices
involved care.
paul
12:37 p.m.
2015-12-01 20:58 GMT+01:00 Joseph Lang <joe.lang.0000 at gmail.com>:
The current loop is actually "proper" .
There are 3 parts to current loop
1) transmitter (switch)
2) receiver (opto coupler in dec stuff)
3) current source
You will have problems if things don't match. An active transmitter has to
connect to a passive receiver.
Passive transmitter to active receiver.
Active means it has a current source,passive no current source.
The 11/05 is active tx active rx. So expects contacts on the keyboard and
the selector magnet in the printer.
Most industrial current loop converters are not this way out of the box.
Now, if this is a VT50, according to my printset it should be passive and
thus if polarity matches should work (unless broken of course). Looking in
the VT52 printset the current loop adapter seems to be configureable using
jumpers for either active or passive. The same goes for the VT1XX option on
the VT100 which had two switches which one could set.
/Mattis
Joe
transmitter, in an electronic terminal as opposed to a mechanical one,
would be a switching transistor that turns the current on and off. The
only issues I can think of are the voltage rating used, and the polarity.
For example, in earlier 60 mA loops (for the Model 15 Teletype and machines
of that era) you might find loop voltages around 100 volts or so, with a
big series resistor. The purpose was to reduce the distortion from the
inductance in the loop (in the receive solenoid). In the later 20 mA loops
I would expect lower voltages to be used. But the specification is pretty
wide open -- "20 mA" is really about all there is. You can build
conforming devices with optocouplers, switching transistors, solenoids and
cam operated switches, etc.
On Dec 1, 2015, at 1:56 PM, Paul Koning
<paulkoning at comcast.net> wrote:
> On Dec 1, 2015, at 1:22 PM, william degnan <billdegnan at gmail.com>
wrote:
>
> ...
> Sorry about the wording of my question. Thanks for the replies. I was
> only able to get the VT50 to receive, I could not send. So I decided to
> research the problem. I found the link above, the author of the page
says
> in effect 20mA did not work (for him) as
desired. So I was wondering if
> anyone here has been successful to attach a M9970 to a VT50 or VT52. I
> spend more time on it, but I was curious if it was even worth it given
the
> hardware.
>
> The author writes:
>
> -start quote--
>
> I first tried to connect a PC with the 11/05 over a industrial
> RS232-to-20mA converter, but this failed.
>
> A 20mA interface works by one side providing a 20mA current, which
drives
> receiver and transmitter of the closed loops
for Transmit and Receive.
>
> But the 20mA interface of the PDP-11/05 is not a proper one: the
receiver
> is more like a low impedance voltage sensor,
while the transmitter
simply
switches
voltage at the levels +3.5V to -15 V. At best you call the
PDP-11/05 serial interface a "TTY interface": it is well suited to read
data generated by mechanical switches to GND, and driving solenoids for
transmit data.
-end quote--
Hm. I wonder by what definition it is not "proper". A current loop
I don't know what "simply switches voltage at the levels +3.5V to -15 V"
means. The voltages at the pins aren't directly relevant, only the voltage
difference between the two transmit pins -- or more precisely, the
resulting current in the loop. I could easily imagine that in the off
state both pins are at -15 while in the on state one goes to +3.5, or
something like that, driving through a resistor of a bit under 1000 ohms.
The fact that the "industrial converter" didn't work does not imply that
the VT50 would have troubles. Just the opposite, actually; I would assume
that DEC would make sure that its 20 mA terminals work with its 20 mA host
interfaces.
Did you check the voltage and current in the two loops when you hooked
it up? I
wonder if you might have the polarity backwards on one of the
circuits, assuming that the devices involved care.
paul
2 Dec
2 Dec
2:31 a.m.
Hi Ethan,
I would be *very* interested on one of those for my 11/05 - including
shipping to sunny Australia :-)
Doug
On 12/2/2015 11:13 AM, Ethan Dicks wrote:
On Tue, Dec 1, 2015 at 3:37 PM, Mattis Lind
<mattislind at gmail.com> wrote:
... should be passive...
The same goes for the VT1XX option on
the VT100 which had two switches which one could set.
I have a couple of the VT1XX
20mA options, if anyone is looking. New in Box.
-ethan
3625
days inactive
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days old
11 comments
7 participants
participants (7)
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