Tuesday, September 6, 2016

More Keyboard Adapters : The Tandy 1000 Keyboard to Tandy 1000 TL or SL

The earlier Tandy 1000s, the 1000, 1000A, 1000 SX and 1000 TX came with a 90-key Tandy Keyboard.  The Tandy 1000 EX and HX had the 90-key Tandy Keyboard built in.  This keyboard uses its own communications protocol and timing and is not compatible with an IBM PC, XT or AT or their clones.  This keyboard uses an 8-pin DIN plug.

The later Tandy 1000s from the TL and SL onward came with 101-key keyboards.  These keyboards, called the Tandy Enhanced Keyboard, were an autoswitching keyboard that could work in an IBM PC, XT, AT or their clones.  This keyboard uses a 5-pin DIN plug and do not work in an earlier Tandy 1000.

In the technical reference manuals for the TL and SL, which are the last Tandy technical reference manuals available online, the keyboard controllers do mention Tandy 1000 Keyboard compatibility.  These computers have a 7-pin DIN connector even though an XT or AT keyboard only uses four pins.  The schematics indicate that the extra pins are used for Tandy 1000 keyboard-specific signals.

I decided to test my TL to see whether this Tandy 1000 keyboard compatibility was real or just a paper feature.  I obtained an 8-pin female DIN connector to plug the Tandy 1000 keyboard into and a 7-pin male DIN connector to plug into the TL.

Here are the pinouts for the Tandy 1000's keyboard :

Tandy 1000 Keyboard

1 - Data
2 - Busy
3 - Ground
4 - Clock
5 - +5v
6 - Reset
7 - NC
8 - NC

And here are the pinouts for the Tandy 1000 TL and SL keyboard's connector :

Tandy TL/SL 7-pin DIN

1 - Clock
2 - Data
3 - NC or Tandy Keyboard Reset
4 - Ground
5 - +5v
6 - NC or Tandy Keyboard Busy
7 - NC Keyboard Type

As you can see, Tandy sought to add signals for the Tandy keyboard around the existing signals for the IBM keyboards.  The conversion I came up with is as follows :

TL/SL - 1000
1     -    4
2     -    1
3     -    6
4     -    3
5     -    5
6     -    2
7     -    3

You will note that pins 4 & 7 on the TL/SL end are both wired to pin 3 on the Tandy 1000 keyboard end.  This is because TL/SL pin 7 determines the keyboard type.  The default is IBM, so you must drive this signal to ground to tell the TL and SL to initialize themselves for the Tandy 1000 keyboard.  This wiring does just that.  Here is the proper pinout for the male version of a 8-pin DIN connector, and the 7-pin DIN is identical except that it omits the center pin :

It was extremely helpful when soldering the adapter to have a multimeter in a continuity tester mode.  This allowed me to ensure that there were no bridged pins and that each wire corresponded to the proper pin.  Also, the mirror image numbering between male and female versions of a DIN connector is very confusing, so I look to the back of the female connector as a male connector.  It is easier to wire a male connector to a male connector.

When I finished the soldering and tested my pins to ensure they were connected properly, I plugged my Tandy 1000 keyboard into one end and my Tandy 1000 TL into the other end of the adapter.  To my amazement, it actually worked!  The keyboard LEDs lit up for a moment, which is always a good sign.  Even the Hold key did what it was supposed to do.  I think I am the first person to ever have attempted this outside Tandy itself!

One thing to note about the SL, the technical reference indicates that U1 must be installed on the keyboard/joystick daughterboard,  The only image of the daughterboard I have seen shows that U1 is present, so it probably won't be an issue.  This is what it looks like with the proper chips installed :

Although the SL/2 is virtually identical to the SL in terms of hardware, I do not know whether Tandy kept the Tandy 1000 Keyboard compatibility throughout the board revisions of that model.  The SL/2 has some differences from the SL, it always uses the updated Bonanza PSSJ chip compared to the SL, early revisions of which used the Jacksboro PSSJ chip.  The SL/2 has a later revision of the BIOS 01.04.04, compared to the SL, 01.04.00.

The TL/2 uses a 5-pin DIN, and according to my friend Cloudschatze, the technical notes for that system state that the Tandy 1000 keyboard compatibility was removed.  The RL, RL-HD, RLX, RLX-HD. RLX-B, RLX-B-HD, RSX & RSX-HD and TL/3 use PS/2-style 6-pin mini-DIN keyboard and mouse connectors and came later than the TL/2, so they are not compatible either.

So why would anyone want to subject themselves to a Tandy 1000 Keyboard when there are so many better keyboards you can use with a TL or an SL like an IBM Model M or a Northgate Omnikey (no adapters required)?  Some Tandy games (King's Quest Tandy booter, Snow Strike) and some Tandy programs (Deskmate through Personal Deskmate 2) refuse to work correctly or will freeze without a Tandy 1000 Keyboard installed.  With the Tandy 1000 Keyboard, King's Quest will not refuse to accept further commands if you turn the sound off by pressing the 1 key.  Snow Strike becomes playable with a joystick on the Tandy 1000 TL, but pressing a keyboard key in the flight mode will give a momentary pause which will not be present on a Tandy 1000 TX or SX.  Without the Tandy 1000 Keyboard, however, Snow Strike would refuse to register any keyboard keypresses after the first one on the TL once you get to trying to fly the airplane.


  1. Hey I have a Tandy 1000 TX computer and I was Wondering if you could help me out, when I turn it on all it does is display how much ram you have and also the floppy drives don't do anything... Let me know what you think, I appreciate your help.

  2. Ask at Vintage Computer Forum or the AtariAge Classic Computer Tandy Computers forum, I and others may be able to help you better in that format.

  3. Thanks I'll look at the 2 sites and let you know what happens, thanks again : )

  4. That is very interesting. Sadly, there are more old-style Tandy 1000 computers without a keyboard. So it would be useful if you could do it the other was round.
    With the research you did, could you build an adaptor to use an SL or TL keyboard - or any auto-switching extended keyboard for that matter - on a Tandy 1000, HD, A, SX, or TX ? I'm sure you could help a lot of people with that. It actually existed: Tandy sold such an adapter, but only very shortly and the info on it (cat nr., ...) is now lost.

  5. That kind of adapter is well beyond my technical capabilities, although I would be the first to queue up to buy one. The official Tandy adapter isn't that great. It only works with XT-protocol keyboards and requires the installation of a special device driver. You would need a microcontroller to receive the raw keyboard scancode from the non-Tandy computer, assign it to a Tandy scancode and then send that to the system using Tandy-capable signaling. The Tandy scancodes are usually the same as the PC/XT scancodes (Set 1), but the timing of the serial bitstream is off just enough to eliminate any chance of an IBM PC/XT keyboard working in a pre TL/SL 1000.

  6. According to the Tandy 1000SX Technical Reference Manual, pins 7 and 8 of the keyboard port are actually used for something, not "No Connection" as listed above:

    1 KBD DATA
    2 KBD BUSY
    3 Ground
    4 KBD CLK
    5 +5 VDC
    6 KBD RST

    Maybe plans for some sort of other I/O through the keyboard port that never got realized?

  7. I think that was the intent, but unless those pins were used in the Tandy 2000 computer, I think it was just an intent that went nowhere. Maybe they had an idea to feed another input through the cable but it never materialized. However, the actual keyboards appear do not connect those pins.

  8. Actually, I'm glad I found this. I too wish to use a T1000 keyboard on my TL. I do have an adapter to use a standard PS2 keyboard on the TL, but like the look and originality of the T1000 keyboards. Thanks for Sharing.