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Terminal for PDP-11/23

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vladstamate

Experienced Member
Joined
Dec 2, 2012
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197
Location
Orlando, FL, USA
Hi all,

I am the happy owner of a PDP-11/23 computer. After the initial tests (the machine has not been powered up in many, many years) and providing stuff does power up, I would like to connect it to a terminal.

Please excuse my noobiness in the questions below. I assume a I need a serial terminal (although my PDP also has a ethernet card). It needs to have a keyboard as well. What kind of terminal should I be looking at getting? Outside eBay where can I look? Can I get something for around $100 or do I need to shell $250+ for a DEC terminal?

I am not (right now at least) interested in getting an original DEC terminal, anything that I can connect to the PDP would be good for me.

Does a terminal like this work: http://www.ebay.com/itm/IBM-3476-In...4152?pt=Computer_Monitors&hash=item4ac5c57d68

How would I connect a keyboard to it?

Thanks in advance for all the help,
Regards,
Vlad.
 
Hi: you should probably tell us which boards you have, the 11/23 could be configured a couple different ways.
But I believe the simple answer is that almost any terminal that has RS232 output should work. There are refinements to this, ie the VT10x had function keys that a lot of programs used, and not all terminals can duplicate. However if I were you I would look into using an old pc with serial ports as your terminal. I believe the are a number of dos based VT100 emulations programs out there that would work fine with your system.

Regarding the keyboard, your 'terminal' sends keyboard data to the 11/23 and recieves the display data on the RS232 line via ascii.
 
Any RS-232 terminal will work for basic communications, and since nearly any terminal ever made after the VT-100 is compatible with it, you shouldn't have much trouble with control codes and such either. Take a look around your local recyclers sometime, and you might be able to pick up a decent '80s or '90s amber-display terminal for cheap or free - just make sure you get the keyboard to go with it, and beware of screens with too much phosphor burn-in (if you see light, clear display patterns when the thing is switched off, you got burn-in!)
 
Terminal emulator or the windows PC communications tool, HyperTerminal will work. Set to serial (com1) 9600 baud. Depending on if your system has a back plate or not you will have a connector for the CON or console port. All commands will pass thru that port and no keyboard connects to the system directly. If everything is working correctly after you push the reset switch on the front of the system you will be greeted with a memory display of 28 and then a “BOOT” prompt. Any peripherals with the system like a disk drive?
 
Hi,

Thank you all for the answers, they are very helpful!

Terminal emulation is what I will going for at first. Also the PDP 11 powered up last night and the power light stayed on. I did it first without the cards in then with the cards.

The PDP 11 does have a back plate but no serial port/CON on it. I do have however a Plessy 3 port serial card. One has the pins cut but the other 2 ports have a 10-pin male configuration (arranged in a grid). Looking at other serial cards for PDP-11 on the net such as DLV11-J they also only have 10-pin ports, so I assume that is standard.

Q1: I assume a need a convertor from 10-pin to RS-232. Would something like this work? http://compatible.eu/index.php?route=product/product&product_id=2424.

Second, my PCs don't have a serial ports anymore.

Q2: Can I use a RS-232 to USB convertor? I assume yes as long as I can set it to COM1/9600 baud.

To answer to Qbus, no, I do not have any other peripherals, just the PDP 11/23 with 5 cards (CPU, men, serial, TK70 controller, DEQNA network). My hope is that after connecting with a terminal to it I will be able to wrote simple programs from console. I am looking for RL-01/RL-02 controller+units so I can eventually load an OS.

Kind regards,
Vlad.
 
One of the plugs on the serial card will have a CON port on it, used that a same adapter before but the wiring for the DB-9 is not the same so had to open up that end and reattach. You will only need pins 2, 3 and 5 (ground).
 
Yes, pins 2,3,5 you are right. I found more info on this page (that matches what you said): http://www.avitech.com.au/pdp-11-03/ba11nc.html.

One problem I have now is that I do not have the manual for my Plessey serial card to find out what jumper settings are needed for turning on "Console Enable" and other bits. I will search over at bitsavers and see what can I find.

Regards,
Vlad.
 
If your plessey card has only three connectors it may be a multifuction MFV11. Is the part number 705115-100? I think two ports are SLU and one is LTC. I don't have any more info than that I'm afraid.
 
Oh I see, SLU are serial ports. In that case I should be able to make them work connecting the way Qbus mentioned.

If I cannot figure out what jumpers to turn on to enable Console mode and if I cannot find documentation I will have to watch eBay for a DLV11-J or a SIGMA 8 port, as bitsavers has documentation about those.

Regards,
Vlad.
 
SLU is Serial Line Unit and LTC is Line Time clock. If this is the only serial card in you 11/23 then I would assume one of the ports will already be setup as the console.
 
Hi all,

So I finally acquired the required cables (serial to USB) and got CoolTerm for the MacOS (and installed the usb serial driver). And I cannot seem to connect. I've followed the instructions from this page (http://www.avitech.com.au/pdp-11-03/ba11nc.html) and connected pins 3 to 3, 8 to 2 , 4 to 5 and 5 to 7. I used wire-wrap technique to connect to the pins on the serial board. When I shorted (I think) one of the cables I got something in the console, so at least I know the serial-usb cable is wired properly.

I assume the reason it is not working is because the serial board is not set up properly to be "console enable". It is possible this serial board was just put in the PDP-11 and not necessary worked with it before. Without the manuals I am kind of lost.

Couple of questions:

1) The "power ok" light is solid on after I power the PDP 11 on but the run button only stays on for about a second then goes off. It does go on again if I press reset but never stays on. Is this something I should worry about? I assumed there is really nothing to run, as no console is connected, but I do not know...
2) If no console/terminal is connected what does the PDP-11 do? Does it just wait there for a terminal to connect to it?

Regards,
Vlad.
 
Also make sure you're using a full null-modem cable to connect from your terminal to the system. Possibly your terminal software needs the modem handshaking (that null modem cables 'fake'0 to operate.
 
I figured out that the KDF11 processor was set (via jumpers) to execute from a fixed address, as opposed to run to ODT/console on power up. So I fixed that, and still nothing. Ah well, I got from eBay a Sigma DLV11-J 4P which has 4 serial ports and I have the documentation for it so I know how to set the switches to turn on console.
 
Sigh...I still cannot connect to the PDP-11/23. I got a Sigma DLV11J-4P for which I have documentation and made sure channel 4 is set to console and all other jumpers are in order (9600 baud, 8 bits, 1 stop bit, no parity, etc, etc) yet I still get nothing on the terminal emulation software (CoolTerm on MacOS). Here is what I have done:

* I left only the CPU board, memory board and the serial board in the slots (3 consecutive slots, in that order).
* I set the KDF11 processor board to drop into ODT and as soon as power on if I flip the halt switch and reset then I get the "Run" light on. I presume the PDP is now running ODT code.

All I get on the terminal is single 16byte of data upon connection: 0xFC or 0xF8 or 0x00. The sad thing is that I seem to receive that even if the PDP is powered off (but cable connected to PDP) and I do not know why.

What exactly is the terminal emulation supposed to receive from the PDP when it powers up? And how long do I need to wait to receive something from the PDP?

I am using serial to USB to connect to the Macbook.

Regards,
Vlad.
 
If you're getting the exact same result when the PDP-11 is on as when it's off, I'd say the problem is likely with your serial-to-USB adapter. Is it a known-good piece of equipment?
 
I'll try to jump in the middle here without doing too much damage to existing conversations.

Things I can think of immediately...

That terminal emulation isn't quite what you need, but let's see if we can prove it's working. It's hard to know what your RS232-USB adapter is like (no pictures) but try this...

1) Bridge TXD and RXD data pins to see if you can at least send characters to yourself and see them on your screen. If that doesn't work, you need to debug that first.

Ok, let's assume that is ok - next

2) connect only Ground and RXD to the target system. Pull everything but the Serial card and the CPU. (no memory needed)

Power the system and see if anything is displayed on the terminal.


I'll check your previous posts to see how the CPU is jumpered and what other settings you've made.

BTW - how are the switches on the front of your BA11 set and what do the lights indicate? (if you posted already - sorry)
 
Ok, I am making progress. On a whim I decided to try to invert receive/transmit pins since I thought maybe the usb-to-serial is not null modem. And behold now I am getting something from the PDP. The prompt is something like this after a reset:

000000
@

Everytime I try to type something though I get this (trying to type vlad)

v?
@l?
@a?
@d?
@

Is this normal? I get the 0000 upon reset and it seems "@" is some kind of prompt.

Regards,
Vlad.
 
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