Hardware Interface Technical Reference, Keyboard 101- and 102-Key

   A capacitive switch works when two plates (usually made of plastic) are connected in a switch matrix designed to detect changes in the capacitance of the circuit. 
   When the key is pressed, the plunger moves the top plate relative to the fixed bottom plate. Usually a mechanism provides for a distinct over-center tactile feedback with a resounding “click.” As the top plate moves, the capacitance between the two plates changes and is detected by the comparator circuitry in the keyboard. 
   This type of switch is nearly immune to corrosion and dirt. These switches are very resistant to key bounce problems that result in multiple characters appearing from a single strike. They are also the most durable in the industry—rated for 25 million or more keystrokes, as opposed to 10 to 20 million for other designs. The tactile feedback is unsurpassed because a relatively loud click and strong over-center feel normally are provided. The only drawback to this design is the cost. 
    Capacitive switch keyboards are among the most expensive designs, but the quality of the feel and their durability are worth it. 

Keyboard Mechanics (Page 162 - 164)
   The keyboard is actually a small computer in itself. The keyboard system consists of a Motorola 6805 microprocessor within the keyboard and an Intel 8042 controller on the PS/2’s planar board. The 8042 keyboard controller directs communications traffic between the computer and the keyboard. The controller communicates with the keyboard via a serial link that supports an 11-bit protocol with parity checking.
   The microprocessor detects depressed keys by scanning the keyboard in logical order and analyzing each key’s status. All keys are classified as being in one of two states: make or break. When a key is pressed, the 6805 microprocessor recognizes the condition and reports it to the PS/2 computer as a key make. It does this by generating an interrupt signal and displaying the scan line number of the key detected. When the key is released, it’s break code is sent to the PS/2.
   The keyboard processor also contains a 16-byte character buffer that allows the keyboard to store up to 16 keystrokes. Should the PS/2 be busy and unable to acknowledge an interrupt, the keyboard buffer safely s remembers the keystroke until the PS/2 has time to assimilate the input. Should you exceed the 16-character limit, the seventeenth keystroke is simply discarded.
   Whenever a keyboard interrupt is generated, the BIOS program queries the keyboard computer for the keystroke number. In order to successfully execute the exchange, bi-directional communications must exist between the two units. Communications between the PS/2 and keyboard are carried out through I/O ports 60h and 64h, input and output, respectively. For every keyboard interrupt, the PS/2 responds with a keyboard query. Data transmissions to and from the keyboard consist of an 11-bit word that is sent asynchronously over the serial data port.
   The keyboard and computer communicate over a pair of clock and data lines. At the end of these lines is an open collector transistor that allows either the keyboard or computer to force the line low. When a keystroke is detected, the keyboard checks the status of the clock line. If the line is low, the keystroke is stored in the buffer and transmission is deferred until a later time. If, on the other hand, it finds the clock line high, the keyboard does a similar check on the status of the data line. When both lines are high, it means the computer is ready to accept data from the keyboard, and the keyboard proceeds to send out it’s 11-bit code. The code begins with a 0 start bit, followed by 8 data bits, a parity bit, and a stop bit. For each bit transmitted over the data line, a coincidence bit is transmitted on the clock line. This clock bit is used by the computer to decode the data bits. Please note that the decoding process can only take place when the keylock on the front panel is on. Keystrokes entered while the keylock is off (keyboard receiver inhibited) will be lost.
   During transmission, the keyboard checks the clock line for a high level at least every 60mS. If the computer lowers the clock line after the keyboard starts sending data, it signifies that the computer is unable to accept any more data from the keyboard. Consequently, the keystroke is returned to the buffer and communications halted until the clock line goes high again.
   Instructions can also be sent from the computer to the keyboard. When the computer wishes to communicate with the keyboard, the PS/2 forces the clock line low for more than 60mS while it prepares it’s message. This action alerts the keyboard that an incoming message is pending. When the computer is ready, it allows the clock line to go high while pulling the data line low. The data is then sent over the data line, which by now has assumed a high-impedance value.
   While all this is going on, the keyboard constantly checks the status of the clock. As soon as the clock line goes high, it begins counting the computer input bits. After the tenth bit, the keyboard forces the data line low. This action signals the computer that the data was received. Each system command or data transmission to the keyboard requires a response from the keyboard before the system send it’s next output. Typically, the keyboard responds within 20mS. If the keyboard response is invalid or has a parity error, the computer sends the command or data again.
   By knowing the timing sequence, it is possible to make modifications to the keyboard through software. This two-way link is vital to the PS/2’s performance. The two-way communications channel is also used to evaluate the well-being of the keyboard’s microprocessor when the computer is first turned on and after each reset operation. (Ed. This is the BAT - Basic Assurance Test).
   When passing data from the keyboard to the PS/2, though, you must be aware that the keyboard’s microprocessor has no idea as to the significance of the keys it is reporting. As far as it’s concerned, the keys have no meaning whatsoever. Each key is assigned a unique 8-bit code which is transmitted to the computer following a make. It is up to the BIOS program inside the PS/2 to decide how the keystroke should be interpreted. The 8042 translates the scan codes it receives from the 6805 to those recognized by the BIOS. The translation table is stored in ROM on the 8042 chip and is not accessible to programs. However, the PS/2 keyboard has the capability of switching scan code sets. In fact, the keyboard offers a choice of three scan code sets. 

International Keyboards (Pages 167 - 168)
   An interesting feature of the IBM PS/2 is it’s international keyboard design. IBM no doubt had it’s eye on a very large market when it conceived the PS/2, and the keyboard reflects this attitude. In fact, the international version of the PS/2 actually has a slightly different keyboard than the US version. Instead of 101 keys, the international keyboard supports 102 keys. This keyboard, which is referred to as the WT (World Trade) keyboard in IBM documentation, is available only outside the US. It differs only slightly from the US version in that it has an additional alphabetical key nestled in the crook of the entry key, which is a larger, hook-shaped key rather than the slim Entry key of the US keyboard. The backslash (\) is located between the Z and the left shift key (as it was on the original IBM PC keyboard). Because the PS/2 cannot distinguish between the two keyboards , the setup software asks the user to identify the keyboard by indicating the shape of the Enter key.
   The reason the PS/2 can support two different types of keyboards is the way the BIOS handles keyboard inputs. As you recall, the keyboard is unaware of the keystrokes it inputs to the system. It simply cites the number of downed key when queried by the 8042 controller chip. It is the responsibility of the BIOS chip to convert the key depressions into ASCII codes and symbols. In the normal default mode, this translates into the US English set of ASCII alphanumeric characters. In the international PS/2 models, another set of scan codes is used to interpret keyboard input.

DOB is 19NOV91 PN 1395601  PCB is 150mm x 38mm

U1 TI 2392161-60425 137 3 Q CK

U2 ST EF6805U3P-B

PCB is 91-ish PCB is PN 1395604

U2 is a Motorola 1394079 (possibly IBM house #)

DOB 31JAN92  PN 1397553  PCB is 150mm x 38mm

  This is a simper design. J3 and J8 have been combined into a 12 pin header, J3.

DOB 20MAR93 PN is 1398012 PCB is 162mm x 50mm

 

U1 TI SN7406N

U2 ST EF6805U3P-B

   CP1 and CP2 (B9HC0114 102MX8) are now back. See the outline for J2 ( four pin header) right below the SDL port?

Pinout for J8
  This little dapper devil switches orientation between horizontal and vertical. The LED tape has to bend on the vertical.

   The Ground trace is almost twice as wide as the other three. The ground trace is always towards Pin 1. 

Rick Ekblaw sent me the original image and said-
   You will notice that this scan is most similar to your PN 1393291 scan.  It is also 170mm x 50mm in size, and the connector layouts are basically the same.  There are some minor layout differences, and the second 7406 open-collector hex inverter and the J10 speaker connector are the obvious additions.  One side of J10 goes directly to pin 6 on the SDL connector, which is why the RS/6000 keyboard cable can not have the "missing pin" found on some PS/2 keyboard cables. 
    The speaker is a little 8 ohm, 0.2W job, IBM part number 1392326. (Ed. I have got to get me an RS/6000 keyboard!!!)

PCB is 1394596

From Gereon Wenzel

SDL = Shielded Data Link, a type of shielded connector created by AMP and used by IBM and others for keyboard cables 

DIN	Signal	KB	+ DCv
1	+KBD DATA	B	4.8-5.5
2	Reserved	F
3	Ground	C
4	+5.0 Vdc	E	2.0-5.5
5	+KBD CLK	D	2.0-5.5
6	Reserved	A
Shield	Frame Gnd	Shield

From Peter Wendt
   Uh ... that's normal. System self-protection you know ... :-) The Elite Keyboard has a different keyboard ID than "normal" keyboards have - and it is intended for "ATX" machines AFAIK and behaves different after a power on. 
   Most likely the 77 Lacuna keyboard controller gets a bit confused by all of that - and hangs the system.  Had that with several Cherry "space saving" keyboards with integrated trackball as well. 

From Jim Shorney
> I was wondering if anyone could help me with finding an inexpensive (i.e. >$20 or less) source for keyboard/mouse emulators. 

   Get a cheap keyboard, take the microcontroller circuit board out, whack the cable to 6 inches or so, and reconnect the microcontroller board. Do the same with a cheap mouse.  Wrap in tape or put it in a small plastic 'project box' to insulate things. 
   The extent of my idea was to provide a small widget that will allow a turnkey system to come up and perform its designated task without needing to have a real keyboard connected, or requiring any operator intervention.  No provision is provided, or needed, to connect a real keyboard in this scenario.
   You might investigate Radio Shack's free cuecat.  It has a keyboard passthrough, and although the barcode reader puts out garbage on a model 95, the hardware may prove useful for your need.

Fools Rush in Where Angels Fear to Tread 
   Is there a way to perform the Dr. Jim Bobbitt method of constructing a emulator that will allow for one to plug in a keyboard, run up the system, do whatever, then unplug the keyboard and walk away?

Holy BAT, Batman!
Tim Clarke scrawled:
> What would the results of plugging a second keyboard into the hacked  emulator? Would the real KB run a BAT as soon as it got power?

   A keyboard *always* sends in a BAT message after power-up, provided that it can control the clock and data lines to it's satisfaction.
   Both the Keyboard and Mouse can be disconnected and reconnected to an IBM PS/2 *after* POST and O/S boot has completed. The (A)BIOS "sees" the BAT message from whichever device and re-establishes current state (as kept in the (A)BIOS data area(s)).
   This is effectively what happens when using a manual KVM. The biggest bugaboo is that there mustn't be a mouse message "in-flight" at the exact instant of disconnection as the PS/2 mouse protocol doesn't have the "start bit" in the first byte of the message, allowing resync if a message is partially incomplete and a new BAT message comes in. Also, the way in which the physical contacts are broken can cause problems whereby spurious message bytes are "seen"/sent. This is mainly a problem with the mouse, due to the multi-byte messages without sync-bit and usually causes the mouse to freeze or, worse yet, leap about the place and cause the buttons to operate incorrectly.
   The above is the situation with direct physical connection (or via a "dumb" manual switch) *and* with O/Ss which correctly use the (A)BIOS to drive the devices at the physical level. WinBlowsHard drivers *don't* do this. Nor do Linux ones, it would seem, although I have no direct experience of this. So the above doesn't apply to Win 3.x, Win9x and possibly Win2K and NT.

Impact of Cutting Data and Clock Lines
Don Hills hanging on to the underside of the earth wrote:
Now, a reading from the Good Book(*)...

   Traffic on data and clock lines is asynchronous - no keyboard pressing or mouse moving, no traffic. Both lines are high when no traffic, and are standard TTL type open collector at each end. So you can break and reconnect the clock and data lines without problems. Just maintain power to the keyboard and mouse at all times- a weakness of manual switch-boxes, especially if you switch slowly or an intermediate position is not used or has a powered-down system on it. If you're building a smart switch box, design it to not switch until the clock and data lines have been idle for half a second or so to make sure you don't switch in the middle of a transmission.

(*)The IBM PS/2 Hardware Interface Technical Reference Manual.

Hold That Thought!
Dr. Jim Shorney has the prescription-
> Could a flip-flop or other IC catch the current state of the data/clock and hold it for the new kb? The idea is to keep the system from detecting the loss of data/clock during the insertion of the new KB.

One thought: grab some 4066 CMOS quad analog switch chips and wire them to tri-state one keyboard while the other is switched through, and vice versa.

   I went to RadioShack and got the casing, as well as a 5 volt blue LED. Forget exactly which one it was--but it is black plastic and the package said something about an RS232 port space.

To mount the keyboard controller inside the casing, I ran a screw through part of the casing and a hole in the controller circuit board.
  As for the blue LED, that was easy. The LED is 5 volts and so is the keyboard supply voltage. So I looked at your keyboard page to get the pinouts, tested with a DMM, and when I found where +5V and a ground came in, I simply spliced in the LED's wires. (Ed. upper two wires, white and yellow)  Then just put the whole mess into the casing, after making place for the LED and cable to come out of.

Helmut P. Einfalt wins for the simplest suggestion:
   Change the <Set configuration>--<Bypass System Programs on Error> to <Enable>. This will give you an error code on the front panel if no keyboard is plugged into the machine, but it will skip over that error and continue booting NT.
   I'm not sure what the system does when you try to plug in a keyboard once it's running... but you might test its reaction to that.

Ed. Not sure what systems have "Bypass System Programs on Error" or similar. I do know some systems have a "Network Server Mode" though.

Al Savage Responds 
   I'm running two OmniViews: one's a four-port SE (I think it's an F1D104, but it's 300 miles away on my server farm right now, running three 8590s and a clone) and a two-port F1D064 here at home.  Both work with 8580s and 8590s routinely with no problem.  I use the hot key sequence on the four-port most often (<Ctrl-Alt-LShift-n>), and the button select on the two-port mostly.  Both methods work. 
   Now, ask me about OS/2, scrollms.exe wheel driver, and the OmniView, and you'll get a different story.  W95 works fine with Intellimouse/Logitech wheel mouse, but not OS/2 w/the OmniView. 

Tim Clarke salvos back 
Hi Al, 
    from the claimed O/S compatibility list for the F1D104 and the problems I've experienced (in both DOS and OS/2) I assume that Win xxx, Linux and Netware all use keyboard drivers that reprogram the keyboard to run in the non-default Scan Code Set 1. If your OmniView "hot-key sequence" is as described, it sounds like you have an F1D074 or earlier firmware. 

From Bob Eager
   Remove the four hex head screws underneath (one needs a long thin hex socket). Detach the cable too. Turn the keyboard the right way up, and remove the top half of the casing. All should be OK. 
   I use a pastry brush to clean it. You can remove most of the keys (except for some of the 'long' ones which are best left alone). Be very careful not to squash the spring when putting the key assembly back. Best to tilt the keyboard, and let the spring 'fall' into the slot in the key as it is pushed in (try it and all will be clear). Take the keytop shells off to clean, of course. 

From Helmut P. Einfalt
   And after you've done that, put all keycaps into an old stocking (ask your better half if she has one with a ladder for you...), knot it so as to keep the contents as loose as possible, and take that bag as well both halves of the keyboard shell to the dishwasher. 
   Wash it with a standard dishwasher program -- you'll not recognize your keyboard afterwards anymore... (And yes, you must take out the electronic innards before washing). If you don't believe me, go ask Don Peter....    Did that on the original PS/2 mouse, too.... Works like a charm. 

From Peter
   Do *not* remove the lower part of the keycaps - only the upper part with the "lettering". The keycaps are a two-part assembly: the "pushrod" and the keycap itself. Remove all keycaps - be careful with the spacebar and the "bigger ones". 

Socket Sizes Needed
From Myself, god-Emperor of Microchannel 
   I used a 7/32 socket - (5.5mm metric size is) a nutdriver or a deep socket. The important thing is something deep enough to fit in the well that most of the screws are in. 

From Peter 
   I got a SKG (Made in Germany) No. 493, 5.5mm Chrome Vanadium. From the "tool wall" of our local super-market for about $3US. Looks like a long screwdriver with a thin walled socket as tip. Works perfectly well since 1987 ...) 

Dr. Jim 
   Speaking of Snap-on, they do carry a nice long socket that works for these.  We bought one for our shop; not cheap, but worth it.  5.5mm, IIRC. 

Allthumbs sez 
   I'm in Canada so the part number may not be applicable south of the border, but this will do the trick. Go to Sears and buy a 7/32" Craftsman deep socket, part number 0942771. You don't even have to buy the 1/4" wrench to fit the socket onto, you can just use the little plastic holder that the socket comes with, because there usually isn't much torque on the screws that hold the IBM keyboards together. Just apply even steady force and you can solve this little problem for about three dollars. (Ed. I now agree after opening up three Model Ms with the socket alone) 

Fixing the detached plastic base

I was delving deeply into the azure realm, when I noticed my Industrial Model M keys were "flexing" before they would do a left Shift-(letter). This was odd, at the time I swapped out the keyboard and thought nothing of it. I finally opened up the case, only to find a goodly number of the melted plastic studs had snapped off, hence the flexing when the key forced the plastic frame down close enough to the curved metal base to create a closed switch...

Searching the web brought up many mods using either wood screws, metal screws, or the omega device, nut and bolt. Being the lazy kind, I asked on the PS/2 Hardware forum for advice. As usual, it came from a man used to the glare of camera strobes and the sighs of starlets that can't catch his attention...

Dr. Jim Shorney takes time from filming infomercials and gives us a prescription:

"Diamond Jim" to his clique, otherwise known as "The Solder God to the Stars" let slip his new Hollywood method of re-attaching the plastic base to the curved metal base:

"The guys that write these nice tutorials don't know about plastite screws. I found a size that works well from McMaster-Carr. Worship me some more and I may enlighten you.

"From the Holy Coffee Can of M-bits...

2-28 x 1/4 TX PLUS HF PT 48 TORXPLUS — T6 Drive
McMaster-Carr SKU 95893A153 50-pack

Also bought #48 and #49 drill bits via ePay to cover all bases."

"Material locks against the triangular (tri-lobular) shank to ensure a vibration-resistant connection. Also known as Plastite screws, they have coarse, sharply angled threads and a blunt tip. They provide maximum holding strength with minimal stress in formable plastics such as polypropylene and polycarbonate. Length is measured from under the head for pan head screws and from the top of the head for flat head screws."

Scan Code Followed by 301 Error

   The first series of the MF-keyboard called MF-1 which lacked the 3 status LEDs had in fact a speaker. It was designed for the XT family of IBM PCs and was intended to be used for "professional typists", which prefered to have a "click" in addition to the mechanical "keyclick" itself. There was a software available, which enables / disables the speaker click ... standard was "On" AFAIK. Worked with that thing for some time back in 1987 ... 
   The MF-II design 101/102 keys *with* the 3 status LEDs inherited the entire case - and the speaker "grille" was left as an artifact and no longer used or needed. Guess it was cheaper for IBM keeping the old molding forms - and produce two keyboards on the same machinery. 

Ian Warford wrote:
  They most certainly are still manufacturing them.  They even (according to the sales guy I talked with) plan on making some black buckling spring 101's next year. Oh, they also make 104 key windows keyboards that feel the same as the old IBM ones :)

Note the manufacture date on my Model M. (Ed. Image edited for size)

. 
42H1292   IBM 101 key buckling-spring KB.   Reg  $79 Sale $49.00 
1393278   IBM "SpaceSaver", heavy-duty 84 key KB Reg $79 Sale $69. 
71G5794  IBM PS/2 Enhanced Quiet Touch KB with 2 Button Mouse