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OpenVMS Hobbyist Program | VAX Systems Forums | VAX Hardware Forum
Author DEC VT320 Terminal
Box_the_Jack_in
Member

Posts: 20
Joined: 27.08.15
Posted on August 27 2015 09:55
Hi, I'm trying to get a VT320 Terminal to send and receive data with a MicroVAX 3100. I seem to have exhausted all the options by trial and error and have tried copying my Liberty Terminals settings (The Liberty does work with the 3100), but all to no avail. I'm getting text on the DECs green screen from the keyboard but no prompt from the 3100, and the delete key doesn't work. It's a perfectly good functioning Terminal and I'm using a cable from OPA0 to the back port of the VT320. Can anyone give me some settings I can put in please, perhaps some that they use with their VAX. I'm sure it's the settings and probably one or two options that need righting.
Thanks for your help
Edited by Box_the_Jack_in on August 27 2015 10:01
Author RE: DEC VT320 Terminal
somersdave
Member

Posts: 67
Location: bristol,UK
Joined: 23.03.07
Posted on August 27 2015 12:49
I recall having problems a few years ago (sorry bit hazy!) with my newly obtained, unknown alphaserver 4000 and playing around with baud rate (9600?) and graphics/serial (which I guess doesn't apply for the micro vax) option at the console prompt but I think all was ok when connecting a VT terminal after obtaining the correct serial cable. I suppose that you've tried the set up (F3?) options.

here's a manual for the 3100 miicrovax I found on the HP site:

http://www.compaq.com/alphaserver/vax/download/ek-mv489-ui-a01.pdf

and some more HP links: http://www.compaq.com/alphaserver/vax/archive/mv3100.html
Edited by somersdave on August 27 2015 12:59
Author RE: DEC VT320 Terminal
Box_the_Jack_in
Member

Posts: 20
Joined: 27.08.15
Posted on August 27 2015 22:39
Hi, Yeah I've messed about with the settings no end and tried 9600 baud. The cable is the right one too and it fits OK in to the OPA0 and in to the MMJ socket on the back of the VT320. I'm not using the serial 25 way D-Type Connector but may try that one. I'll also see what the settings in VMS are and play about with those too. Do you know any company that sell MMJ to MMJ leads or perhaps custom make them please? Thanks for the links, very useful smiley
Author RE: DEC VT320 Terminal
abrsvc
Member

Posts: 107
Joined: 12.03.10
Posted on August 28 2015 01:26
Please post the settings you are using for the VT320. These should work in the "default" mode with the VAX. Typically 9600 baud, 8 bit with no parity.
If you have the wrong connector, it will fail though. Do you have the DecConnect cable from the VAX to the terminal or is there an adapter (MMJ to 23 pin)? There are a number of different MMJ to 23 pin connectors which may be the problem here.

Dan
Author RE: DEC VT320 Terminal
Box_the_Jack_in
Member

Posts: 20
Joined: 27.08.15
Posted on August 28 2015 09:51
Hi Dan, I'm using MMJ to MMJ and it's possibly the cables fault. I've tried the default settings and no go. The settings that were promising were 9600 baud, 8 bit no parity, 1 stop bit, cable to cable connection, echo on, on line, vt 320. With this and many other settings I get the ability to type and return and the screen scrolls but I get no $ prompt. I will try the MMJ to 25 Way D-Type as I've just ordered three gender changers so I can try the cable I use with my Liberty terminal on the VT320. I'll also explore the settings in openVMS itself as these may need changing. I've spent a few hours trying out settings. It amazed me as the Liberty you just plug in and it seems to work with most settings, which makes me think it's the cable.
Ian
Author RE: DEC VT320 Terminal
malmberg
Moderator

Posts: 527
Joined: 15.04.08
Posted on August 28 2015 14:42
The first thing to test is a loopback on the terminal. If you have a defective or fragment of a MMJ cable, then you can easily make a loopback.

Otherwise get a MMJ to D adapter.

You can also modify a RJ45 connector to remote the tab to make a loopback.

A correctly made MMJ cable has a "twist" in it so that you can use it between two DTE devices such as a terminal or a computer. In some cases "home" made cables were made with out the twist.

There are multiple MMJ / D sub adapters out there, so be careful to find out the pin-out for your test.
Good Luck.
Author RE: DEC VT320 Terminal
Box_the_Jack_in
Member

Posts: 20
Joined: 27.08.15
Posted on August 29 2015 05:39
Hi Malmberg, I did wonder about the quality of the cable as it seems to be very flat looking. I'm just going to try it now with an MMJ to D adapter as my gender changers have arrived in the post.
Thank you very much for your help.
Author RE: DEC VT320 Terminal
abrsvc
Member

Posts: 107
Joined: 12.03.10
Posted on August 29 2015 06:29
The "original" cables that had the MMJ connectors were all FLAT cables. It is important to note that there are different cables though. Some had the "twist" and some did not. You need the one with the twist. These were often known as null-modem cables.

Dan
Author RE: DEC VT320 Terminal
somersdave
Member

Posts: 67
Location: bristol,UK
Joined: 23.03.07
Posted on August 30 2015 02:25
To clarify something (for myself anyway!) the only connection option between the microvax 3100 and the VT320 monitor APPEARS to be via MMJ connectors - whereas later VT420 and VT510 (which I was very kindly given) have both the option of MMJ or 25 pin connector with my alphaserver 4000 having the 9 pin console port.

I found what appears to be a typical piece of 'typical' flat "DECCONNECT OFFICE CALE E80094" and a company which may be able to give some advice and supply components (there are probably others):

http://www.stanq.com/cable.html - better say "courtesy of Quayle Consulting Incorporated" as it's copyrighted info.

for more usual cables and cable 'adaptors' I found this company in the UK had a good supply of components at a reasonable price and gave good service when going through a similar exercise:

http://www.solentcables.co.uk/acatalog/Computer_Cables.html

One final (missing) Youtube link I found, here's a guy who has linked his VT320 to a Linux machine (I think) with some musical accompaniment :
https://www.youtube.com/watch?v=jNLPg5JE7no
Edited by somersdave on August 30 2015 06:13
Author RE: DEC VT320 Terminal
Box_the_Jack_in
Member

Posts: 20
Joined: 27.08.15
Posted on August 31 2015 13:36
Thanks Dan that seems to confirm what I've found out about the flat cables. I still haven't had time to try my cable that's connected to my Liberty Terminal, with a male to female gender changer in the 25 pin D-Type port at the back.

Great links Dave and very useful thank you smiley I believe certain models of the VT320 didn't have the 25 D-Type on the back. Mine do have and there is an option in my Setup screen for a VAX MMJ to the 25 D. Haven't tried it yet though smiley You can also use the 25 D with a modem and a printer I believe.

Ian
Author RE: DEC VT320 Terminal
malmberg
Moderator

Posts: 527
Joined: 15.04.08
Posted on September 01 2015 03:04
In a perfect MMJ world, all cables should have a "twist" in them. You use a DCE or a DTE adapter when connecting them to something that is using a D connector.

In a perfect D connector world, all DCE devices have female connectors and all DTE devices have male connectors. DCE devices are modems, DTE devices are terminals, printers, terminal servers and computers.

A common error in home made MMJ adapters is not connecting one of the two signal returns. With the twiist in the cable, and this error on both ends, there is no signal return at all. Yet it usually mostly works, only because the return signal is going through the safety ground in the power cord.
If you have a MMJ-D adapter with out connecting both signal returns together, it is defective.

Known MMJ-D sub adapters:

9-pin VAX (old) DTE only.
9-pin PC/Alpha (newer) DTE only. Signal return on different pin than above, so sometimes "works" for the VAX adapter and vice-versa.
25 pin DTE Male, supplies with terminals
25 pin DTE Female, supplied with Digital branded printers that had female connectors. (rare)
25 pin DCE Female, for use with modems.

Null modem adapters were mainly needed for commercial pre-made cables that were designed for terminal to modem or CPU to modem, so had a male connector on one end and a female connector on the other. It was hard to find a pre-made null modem cable with two male connectors in the catalogs. Apparently either sites made them themselves, or bought the relatively expensive null modem adapters.

For standard equipment using D connectors, if the RTS and CTS are not wired through, they should be jumpered together. If the DSR and DTE are not wired through, they should be jumpered together.

On DTE devices on the computer side, if the CD is also not wired through, it should be jumpered to the DTE signal. While you may get away with out doing these things, some software and hardware will not work unless some of the above are done. Terminals and printers, and terminal emulators generally ignore the CD signal.

A modem on a cable with the DSR/DTE/CD jumpered is insecure.

Any other wiring pattern for D connectors is only needed if the equipment is non-standard. I have seen one printer that required the one of the input pins it should have been ignoring jumpered or it would stop printing after a paper jam, and I have a HAM packet modem model that has the RTS and DSR pins swapped internally. So on occasion you do need something special.
I would make sure that the connectors are properly labeled.

I picked up a an unknown to me brand terminal for $1.00 at an auction a while back. It claims a VT220 personality, but it only works with the cable that came with it. It does not work with a standard cable, and I have not had time to trace out the wiring of that cable, as I have not been using real terminals for a long time.
Author RE: DEC VT320 Terminal
Box_the_Jack_in
Member

Posts: 20
Joined: 27.08.15
Posted on September 01 2015 04:51
Hi Malmberg, It's like my Liberty Terminal I managed to get three really cheap at an auction. Two were very discoloured and orange, and one didn't work and one works fine and the other is so- so in usability. They're great Terminals and don't have MMJ but a 25 D-Type female so I had a couple of 10 foot leads custom made for them. They're amber screens. The reason I want to use the DEC VT320 is they have green screens and such a lovely clear picture. I'll get them to work as I've a cable on the way shortly from a guy who I bought a VAX from and he used it with a VT520. I think the problem is getting the MMJ plugs and the 25 pin nowadays as they're legacy (as much technology is becoming) so even if a cable manufacturer wants to make you a cable to order, those are the two bits he doesn't have! I seem to think that some of the old Apples like the original iMac insisted on twisted 'ethernet,' cables or they wouldn't work with a router for Broadband. Quite a lot the cheap ethernet cables do work though with PC's and modern Macs. It seems the DEC stuff is quite choosy for data communication. Reading your post I know a bit more why now!
Thanks smiley
Ian
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