finding a white paper on PS/2 port

[tiebird321]

I'm trying to find the origional white paper spec for the PS/2 port
google and yahoo have failed me so i'm hoping someone else might refer to these things reguarly and know where i can find a copy

i'm specificly trying to figure out if the PS/2 port spec specificly includes backwards compatability with the AT keyboard spec

I just (tried to) deploy)ed( 30 new slim terminals in a data entry centre, the terminals claim to be PS/2 complaint. however using the old IBM battleship AT keyboards with them (the employe's have said if they go away they will strike) has led to big issue's.
The keyboards have been varified on over 30 other systems and worked perfectly on all of them (using a normal AT->PS2 adapter).
On these new terminals they are acting eraticly, randomly adding in key strokes or missing some and acting like the shift/alt key was being presed even when it wasn't being touched

I thought that AT compatability was built into the PS2 spec. so if someone can prove me wrong or right i am going to be very gratefull

 

[Elledan]

The information I've described so far in this page applies to modern keyboards, which is anything from the mid-1980s on. The old 83-key keyboards used on the first IBM PCs and early clones were somewhat different electrically from the keyboards we use today; the primary difference is that they were unidirectional--only able to receive data from the PC, not send it. You cannot generally mix modern keyboards with these old keyboards. For a while--especially in the late 1980s when many of these original PCs were being used side by side with newer AT and later models--keyboards often came with a physical switch on the bottom to select either "AT" or "PC/XT" signaling. Today most keyboard makers no longer bother with these switches, the PC/XT being long beyond obsolete.

http://www.pcguide.com/ref/kb/const/opSignaling-c.html

The keyboard interface is a serial link, of which the specifications haven't changed since the above mentioned PC/XT spec.

Methinks there's something else going on, probably related to those terminals. It might be that the spec is implemented more strictly by either the terminal or keyboard, leading to synchronization and communication issues.

Do other keyboards work fine with those terminals? Try some other old keyboards with DIN-connectors as well.

 

[stevewm]

AT and PS/2 are not different protocols. They are electrically identical. The only difference is a different plug! And there really is no official standard for the keyboard interface. Its what IBM originally used, everyone else just followed along since IBM was "the thing" back then. And if I remember correctly, the only actual printed documentation on the protocol was some IBM technical reference manual...

Now to the problem at hand.....

I can only assume you are talking about the famed IBM Model M line of keyboards. Unfortunately IBM Model M's have a slight problem that causes many modern motherboards and most PS/2 to USB adapters to not work properly with the keyboard. The symptoms include random keystokes, modifier key states randomly changing, Num/Scroll/Caps indicators not working, and/or the system failing to detect the keyboard at all.

The only way to fix this is to modify the keyboard.

http://www.geocities.com/jszybowski/keyboard/

The above page details what the problem is and the fix that you will have to do. I have sucessfully done this to all 3 of my IBM Model M keyboards after I discovered some of the machines I where bringing in to fix would not detect my keyboards! I did the mod on the keyboard PCB. But at that page mentions it can also be done inline on the cable somewhere.

 

[Elledan]

Thanks for the link, stevewm! I've got a couple of model Ms myself, so I might need this information in the future

 

[tiebird321]

I can only assume you are talking about the famed IBM Model M line of keyboards. Unfortunately IBM Model M's have a slight problem that causes many modern motherboards and most PS/2 to USB adapters to not work properly with the keyboard. The symptoms include random keystokes, modifier key states randomly changing, Num/Scroll/Caps indicators not working, and/or the system failing to detect the keyboard at all

Actualy they are Omni Key Ultra's (made by Northate computer systems) they were sold for in excess of $170 for a basic, and up to $300 for the ultimate one that is my personal one
these things are impossible to find.
especialy the higher end ones that were BOTH AT and Apple serial compatable.
they are very similer to the M series, just very few people know about them so i generaly just refer to them as the battleship and it works out fine

I checked with an engineer at the MANU of the terminals and confirmed the units are only rated for 50-90ma of power and these things are perently worse power hogs than the IBM M's
so after deploying 30 USB->ps2 adapters everything works great

The sales rep sucked the $280 charge intead of taking the units back so everything is happy

thank you all very much for the help