3151 ASCII Display Station

187-132 3151 ASCII Display Station
189-071 New Models And Enhancements (510/560 and 610/660)
Common Problems and Questions About 3151 Terminals

3151 Models (a bunch of tables)
3151 Errors (stub)

GA18-2633-0 3151 ASCII Display Station Guide to Operations May, 1987
GA18-2634-0 3151 ASCII Display Station Reference Manual Apr, 1987
GA18-2654-0 3151 User's Guide for Cartridge to Emulate IBM / DEC Terminals Apr, 1987

CONSOLE_fix_T4.zip Makes the "ASCII Terminal" option available (more info HERE)

IBM 3151 ASCII Display Station
3151 / 3153 Keyboard
Communication Ports
ASCII Terminal on the 8595 / 9595 / 95A
Missing ASCII Terminal Selection
Video Calls under Console Mode
Can Serial Console Support be Added to a Model 90?
Opening and Closing the 3151

IBM 3151 ASCII Display Station

The IBM 3151 ASCII Display Station is a two-element workstation that provides attachment capabilities to both IBM and non-IBM processors. A native mode and 10 non-IBM emulation modes are included in the base of all models. The Model 110 should be used for entry level applications requiring an 80-column display. Models 310 and 410 (which are functionally identical to each other except for the color of the display phosphor) should be used with applications that require 80- or 132-characters-per-line capability, 3101 emulation, a dedicated numeric keypad, Program Access (PA) keys, greater than 12 function keys or RS422A capability via cartridge. Additional emulations and attachment capabilities are provided in two new slim-line cartridges for Models 310 and 410.

The IBM 3151 Cartridge for Emulating IBM and DEC Terminals provides the ability for IBM 3151 Models 310/410 and 360/460 to support RS422A communications for the emulations provided on that cartridge. The RS422A interface supports a point-to-point direct coupling with a maximum cable length of 4,000 feet.

The main communications port has a selectable transmission rate from 50 bps to 38,400 bps, inbound and outbound XON/XOFF pacing (inbound pacing is the default and not selectable), and echo/character/block modes, and supports seven- or eight-bit word length and no/odd/even/mark and space for parity.

The auxiliary port on the 3151 Model 110/160 is a unidirectional RS232C port for attaching another asynchronous ASCII device such as an ASCII printer. On IBM 3151 Models 310/410 and 360/460 the auxiliary port is enhanced with a bidirectional data capability. This allows the attachment of output devices, such as a printer, as well as input devices, such as wands and ASCII terminals. Transmission rates from 50 bps to 19,200 bps are selectable independent of the main communications port speed settings.

3151 / 3153 Keyboard

The 3151 and 3153 keyboards are not interchangeable. The following is a diagram of the modular RJ keyboard connector:

Pin 3151 Signal Name Pin 3153 Signal Name
2 +5V 3 RESET*(pulled up to +5V)


These pins and connector drawing are relative to the connector on the 3151, 3153 video element. These pins and connectors are not relative to the connector on the keyboard coiled cable.

Note: Even though the 122-key terminal keyboard is not officially supported by the 3151, it works just fine.

Communication Ports

If you look at the back of the 3151, the main port is on the right-hand side, closest to the edge. The auxiliary port is closest to the power cord.

ASCII Terminal on the 8595 / 9595 / 95A

The 8595 / 9595 / 95A supports the specialized use of some ASCII display stations instead of a display and a keyboard. The following IBM ASCII display stations can be attached to a serial port: 3151, 3161, 3162, 3163, and 3164.

Keep in mind if you plan to use an ASCII display station:

  • Verify operating system supports an ASCII display station. Not all do.
  • BASIC language is not supported.
  • High-resolution graphics (icons and graphic-based programs) are not available.
  • Power-on self-tests (POST) text messages and logs are not available.

Use the setup instructions that came with your ASCII display station and the information in this section to attach it to your server.


  1. Use a null-modem cable or adapter. Without one, the ASCII display station has no communications link with the server.
  2. If your ASCII display station has a test switch next to the keyboard connector, make sure it is in the normal position, not the test position.
  3. When using system programs to define setup values on the ASCII display station, be sure terminal machine mode matches the actual display station. Example, if installing a 3151 ASCII Display Station, you must set Machine Mode on terminal Setup Menu to IBM3151. When the setup values correctly match the display station type, the machine is considered to be in the native-machine mode.

To set up your ASCII display station

  1. Attach null-modem cable [or adapter] to the ASCII display station. Connect the other end to one of the serial connectors on the server.

    Note: For 95A systems, if serial port power-on mode is enabled, attach the ASCII display station to serial port B.

    Connect power cord to server; then plug it in.
    Connect power cable to ASCII display and plug it in.

  2. Turn on ASCII display station [is it in native-machine mode?]. (See note 3)

  3. Set the communication values on display station:

    1. Press Ctrl and Setup to display General Setup Menu.
    2. Press Send to display Communication Setup Menu.
    3. Review communication values and compare them to the values shown below.
    4.          Line Speed (bps)             9600
               Word Length (bits)              8
               Parity                         No
               Stop Bit                        1

    5. To change a value, move cursor to highlight it, then press space bar to display alternative values.
    6. When all communication values match the values specified in this section, press Send twice to display Function Menu.
    7. Move the cursor to Save data field and press space bar to store these values.


    1. When using system programs, do not install an emulation cartridge unless it will support native-machine mode.
    2. The display stations designed for countries where English is not the native language must support the ISO 8859/1.2 code page. Some display stations require a cartridge to support this code page.
    3. For additional information about communication values, refer to the documentation that was supplied with your ASCII display station.
  4. Verify that all the correct values have been stored:

    1. Move cursor to Recall data field. This displays current communication values. (Your server uses these during configuration process.)
    2. Press Ctrl and Setup to exit. Only the cursor will be displayed on the screen.

  5. Start system programs.
    • If you are using an ASCII display station:

      1. Insert Reference Diskette in diskette drive.
      2. Turn on ASCII display station and server.
      3. When cursor moves to top-right corner of screen, press and hold Ctrl + I (the letter "i") to view Main Menu of the system programs.

  6. If you are using a keyboard and a display:

    1. Insert Reference Diskette in diskette drive.
    2. Turn on server and allow POST to finish.
    3. Press F1 to view Main Menu of system programs.
  7. Change Console Select settings to select an ASCII display station.

    Warning! Before making changes using Console Select program, make sure you have an ASCII display station attached to server. If you do not, there will be no way for you to communicate with the server.

    When you are at Main Menu,

    1. Select Set features; then, press Enter.
    2. Select Set console from the Set Features Menu; then, press Enter.
    3. Select ASCII display station from Set Console Menu; then, press Enter.

  8. Make sure the values are set as shown:

             Baud rate               9600
             Bits per character         8
             Parity                  None
             Stop bits                  1

    Any time you change the ASCII display station values, you must also update the system unit values to match. The baud rate should always be 9600 or above. If you set the baud rate below 9600, the system performance decreases.

    Note: These instructions assume that the display station has already been set to these values (see step 3 of this procedure).

Some server operations change when you use an ASCII display (see the following).

Communication When using an ASCII display station, the communication parameters will appear on the 95's information panel (example, 96-8N1). This is not an error message.

Configuration When you run the server setup programs, system programs, or diagnostics programs from the ASCII display station, the display station values might change. If display problems occur after you run these programs, check the display station values. To check these values, press Ctrl and Setup. Modify the values if necessary.

Utility Programs To start the server system programs when using an ASCII display station, insert the Reference Diskette into the startup drive. Turn on your server.

Note: To restart your server after running the utility programs, press and hold Ctrl, then press C, A, and D. Release C, A, and D. Then, release Ctrl.

Diagnostic Tests When you select an ASCII display station as the system console, the keyboard, mouse, system board async port, and video displays will not on the diagnostic Installed Device list.

Missing ASCII Terminal Selection

Anyone know why I don't have the option for an ASCII display under Set Console? I tried it on my 9595-0LF and 9595-3PT. Neither one has it. The 9595-0LF did go into "96-8N1" mode by itself about a month ago but it won't now that I want it to!

I have a "IBM Cartridge to emulate IBM and DEC terminals" P/N 94X4114. Of course nothing works with or without it installed...

Hi Dennis!
   You need a nullmodem cable for the terminal and no cartridge installed (native mode). The terminal test switch must be in "normal".

There should be a chapter on using the ASCII console in the EPRM...


The 9595 should be configured to "keyboard and videoless mode" somewhere in additional features. Then the video card must be removed to force the machine to kickstart the ASCII-terminal at COM1.

Issue Fix (by Major Tom)

The "ASCII Terminal" option is not available because of a bug in the CONSOLE.COM program on the reference disk. The utility calls Int 15 func. 3Dh subfunc. 01h and then checks bit 17 of reg. EBX. Based on its value it then allows or disallows the two additional console options: "ASCII Terminal" and "No Console". The problem with this is that the bit in question is *never* set for any of the supported planars (the bitfield is hardcoded and never modified). This check is not present in any other version of the CONSOLE.COM utility (afaik). It's possible that the CONSOLE.COM code is actually correct and it's the BIOS bitfield what's wrong, but the result is the same and the CONSOLE.COM program is easier to fix.

I've modified the CONSOLE.COM binary so it checks bit 16 instead - bit that is *always* set for the supported systems. You can download the patched binary HERE. Extract the file and copy it to your Type 4 reference disk, replacing the original file. You can then optionally run the "Update System Programs" option to copy the new file to the convenience partition on your hard-drive.

Video Calls under Console Mode

Major Tom has conducted painful probulation and reports:
   In the console mode they are overriding all video calls (Int 10) with a special table that transforms it to some special serial port calls (undocumented Int 14 functions 60-64 - exclusively used by the serial console code), and they are doing some magic with keyboard buffers as well. I think the serial console mode should work fine in most "well behaved" text mode applications.

That's what I wanna test... It will also help me figure out meaning of some of the CMOS, NVRAM, and EBDA fields.

Quick & dirty list of the undocumented Int 14 functions:

Int 14 AH=60h - Initialize and attach CONSOLE Device
Int 14 AH=61h - CONSOLE Input
Int 14 AH=62h - CONSOLE Output Character (AL - char)
Int 14 AH=63h - CONSOLE Output String (ES:SI - string ptr)
Int 14 AH=64h - Remove CONSOLE Device

Incomplete and not quite confirmed yet, I will have to put more work into this. The serial console stuff is not a priority, and I'm just mapping what is what at this point.

Ed. Tom: This has since been confirmed by the US5193174 patent, names of the listed routines were modified to match the "official" ones.

Can Serial Console Support be Added to a Model 90?

The serial console mode is explicitly disabled on Model 90 directly in the POST code. It checks the planar ID, and if it's FF6Fh, it completely skips the serial console initialization code. Not sure if there is any technical reason for this, or if they did it just for market segmentation reasons, but I could easily patch the ROM to see whether that's enough to enable the console on Model 90.

Some other patching may be necessary though, as to enter the console mode on my 9595 I had to physically remove the video adapter from it. Changing the console settings, and disconnecting my keyboard and/or monitor wouldn't do it. And Model 90 has the always present on-board XGA... Maybe this was just a PEBCAK though, as I didn't have much time to play around with it.

Ed. Tom: It's possible to force the ASCII terminal mode with a fixed CONSOLE.COM binary (see HERE).

So, the serial console mode may be possible on some of the late PS/2 machines (will have to check the ROMs), but it would be fairly difficult to add it to the older systems. There is A LOT of code related to the console mode in the ROM, and it's spread all over the place. Even thinking about backporting all that to the older POST/BIOS code gives me a headache.

Opening and Closing the 3151 (by Major Tom)

If your terminal has the optional tilt stand, remove it first (it's locked in place by two plastic latches, see Guide to Operations page 26 physical for details).

The entire case is held together by a single screw and two large plastic clips. First, you need to undo the screw at the bottom of the case... which is where the first problem comes up. The screw has a round, completely smooth, head with rounded edges. To make things even more complicated, there's a plastic ring around the screw (see the pictures below).

Probably the easiest way to remove it would be to take a Dremel and cut a groove into the head (don't cut too deep, we don't want the head to split), and then use a flathead screwdriver to undo it. Be aware that this method will likely damage the plastic ring around the screw unless you have a cutting wheel with a very small diameter and really steady hands...

Alternatively, you can try grabbing the head with a pair of fine nose pliers (small wire cutters could work as well) and unscrew it that way. It helps if you mark the head with a sharpie or something, so you can tell if the screw is actually turning or just slipping. If you are lucky the screw isn't in too tight, and if you manage to turn it a bit, you are pretty much set, it only gets easier as you go. This is the method I've used and it took me probably 5 minutes to remove the screw, with a minimal damage to the screw "well". You can press on the plastic to make it bend inwards and give yourself an extra millimeter of depth to work with. YMMW.

The annoying anti-tamper screw

And the winner is... nose pliers!

With the screw removed, you should be able to split the bottom side of the case - don't open it too much however, you could break off the plastic tabs at the top side of the monitor (they would probably unclip before breaking, but the plastics are getting brittle, so I wouldn't risk it). Normally there are two openings that can be used to unclip the tabs, but not here! Wegh... turn the monitor around, so you can access the top side easily and try shoving a piece of plastic or paper (i.e. a business card, or a credit card if it fits...) between the two halves of the case (towards the front face) starting in the corner and working it towards the center. The two tabs are only some 3 cm from the corners and about the same distance deep. This way you should be able to unclip one side and then the other, setting the back cover free.

Something tells me that IBM doesn't fancy the idea of you poking inside one of these things very much...

Warning: The picture tube acts as a large capacitor and can hold a charge of several thousand volts for prolonged periods of time! Discharge it with a grounded screwdriver before removing the anode cap! The capacitors on the PCB can be charged to a few hundred volts! Improper manipulation may lead to an injury, death, fire, and/or other damage. The author is not responsible for your actions and their consequences. Proceed at your own risk!

The internal metal shroud is not held in place by anything but friction, and the same is true for the PCB (be careful when removing these items, you don't wanna "neck" the picture tube!). The entire thing is rather cheaply made. There's a single board inside that holds the PSU, the flyback, the digital circuits, and even all the connectors and controls. The backup battery is solder in, the serial connectors lack the metal shielding... certainly not up there with the PS/2 line quality-wise.

When putting the thing back together, make sure that the PCB is seated correctly inside the case - the front controls must be aligned with the front panel openings. The metal shroud goes *over* the metal tabs that are attached to the PCB, not the other way around. Before you clip the case together, check that the serial connectors, the card slot, and the power socket are all aligned with their respective holes.

Much better...

And finally, replace the annoying "anti-tamper" screw with a normal one - try to match the diameter and thread pitch if possible.

The original is: AVSAFE (thx Louis) self tapping screw, d=4 mm, l=13 mm (w/o head), head d=7 mm.

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