Wout Mertens' Guide To Keyboard Programming v1.1 Complete
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Table of Contents
?????????????????
0 Legal Info
0.1 Preface
1 Overall Information
1.1 Extended ASCII
1.2 Special Functions
2 DOS Interfacing
2.1 Functions
3 BIOS Interfacing
3.1 Functions
3.2 Keyboard Flags
3.3 Keyboard Buffer
4 Low-Level Interfacing
4.1 Interfacing And Configuring
4.2 Lay-Out
4.3 Scancodes
4.4 Int 9
5 Tech Stuff
A Acknowledgments
B How To Contact Me
C The Answer To Life, The Universe And All The Rest
D History
0. Legal Info
?????????????
This "Keyboard Guide" is (C) Copyright 1994 Wout Mertens.
All rights reserved.
THIS DOCUMENT AND THE ACCOMPANYING SOURCE CODE FILES ARE PROVIDED "AS
IS" WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING ANY
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WOUT
MERTENS WILL NOT BE HELD LIABLE FOR ANY DAMAGES OR LOSSES OF ANY KIND
THAT RESULT FROM THE USE OR THE INABILITY TO USE THE INFORMATION
PROVIDED IN THIS DOCUMENT OR THIS SOURCE CODE FILE, INCLUDING, BUT NOT
LIMITED TO, LOSS OF PROPERTY OR INCOME.
This document and its accompanying source code files are freeware, not
public domain. They may be distributed freely provided that neither
file is modified, and that they are distributed together along with
FILE_ID.DIZ in their entirety, including the legal notice, and that:
If they are distributed by a third party vendor, no more than $5 U.S. is
charged for the disk on which the archive, containing this document and
the accompanying source code files, is stored, except when distributed
on CD-ROM.
This legal information supersedes all previous notices.
0.1. Preface
????????????
I wrote this document because I needed info, and thought I could get it
this way. Boy was I wrong! I ended up finding it all by myself. Anyway,
I hope you can use it. It is meant for people who know what interrupts
are and that 0ah equals 10. Enjoy.
Oh, almost forgot. I didn't give this text any page formatting (aside
from spaces before and room after for ease of reading) because:
- I read ALL my documents on-line
- People have differing page sizes and then it would look like
shit for some people and too short for others.
If you want to print this, well, go ahead and format it, BUT DON'T EVEN
*THINK* OF SPREADING IT !!! (Except when you ask my permission)
Everytime you see something like d9h or 65h, it is a hexadecimal
number. No trailing 0 was added for ease of typing.
1. Overall Information
??????????????????????
On the IBM, there are three ways, all alike, to access the keyboard.
Via the operating system, via BIOS or via low-level access. Which way
you use depends very much on the application you are writing. Games do
not use DOS functions, for example. And a file-compressor is really not
interested wether you are actually pressing 'Y' or not. Or how long.
This is the way it works:
Hardware ??????????????? BIOS ???????????????? ????? DOS ???
??????????????
?Keyboard Data??????
???????????????? ?
?????? ??????? ????????? ? ?????????????? ?????????????
?key- ????int 9????keyboard????BIOS keyboard????DOS keyboard?
?board? ? ??????? ?buffer ? ? ?functions ? ?functions ?
??????? ? ?????????? ? ??????????????? ??????????????
? ? ? ? ?
??????????????????????????????????????????????????
?
Possible tap points
The keyboard triggers IRQ 1 (Interrupt Request), also known as int 9.
Int 9 then translates the keyboard codes into ASCII, or when necessary,
extended ASCII, and places it into the keyboard buffer. Also, the shift
and lock states are saved in the BIOS Data Area (seg 40h). The keyboard
buffer is then used by the BIOS functions to interface with programs.
The DOS functions use the BIOS keyboard functions to interface with
programs as well, but on a higher and more protected (Ctrl-Brk etc)
level.
1.1. Extended ASCII
???????????????????
Extended ASCII is IBM's way of letting non-ASCII keys be recognized by
programs. The BIOS will first send 0 and then the extended ASCII code.
Here is the table:
?????????????????????????????????????????????????????????????????
?Key Hex Dec?Key Hex Dec?Key Hex Dec?Key Hex Dec?
?????????????????????????????????????????????????????????????????
?F1 3B 59?Shift-F1 54 84?Ctrl-F1 5E 94?Alt-F1 68 104?
?F2 3C 60?Shift-F2 55 85?Ctrl-F2 5F 95?Alt-F2 69 105?
?F3 3D 61?Shift-F3 56 86?Ctrl-F3 60 96?Alt-F3 6A 106?
?F4 3E 62?Shift-F4 57 87?Ctrl-F4 61 97?Alt-F4 6B 107?
?F5 3F 63?Shift-F5 58 88?Ctrl-F5 62 98?Alt-F5 6C 108?
?F6 40 64?Shift-F6 59 89?Ctrl-F6 63 99?Alt-F6 6D 109?
?F7 41 65?Shift-F7 5A 90?Ctrl-F7 64 100?Alt-F7 6E 110?
?F8 42 66?Shift-F8 5B 91?Ctrl-F8 65 101?Alt-F8 6F 111?
?F9 43 67?Shift-F9 5C 92?Ctrl-F9 66 102?Alt-F9 70 112?
?F10 44 68?Shift-F10 5D 93?Ctrl-F10 67 103?Alt-F10 71 113?
?????????????????????????????????????????????????????????????????
?????????????????????????????????????????????????????????????????
?Key Hex Dec?Key Hex Dec?Key Hex Dec?Key Hex Dec?
?????????????????????????????????????????????????????????????????
?Alt-A 1E 30?Alt-P 19 25?Alt-3 7A 122?down 50 80?
?Alt-B 30 48?Alt-Q 10 16?Alt-4 7B 123?left 4B 75?
?Alt-C 2E 46?Alt-R 13 19?Alt-5 7C 124?right 4D 77?
?Alt-D 20 32?Alt-S 1F 31?Alt-6 7D 125?up 48 72?
?Alt-E 12 18?Alt-T 14 20?Alt-7 7E 126?End 4F 79?
?Alt-F 21 33?Alt-U 16 22?Alt-8 7F 127?Home 47 71?
?Alt-G 22 34?Alt-V 2F 47?Alt-9 80 128?PgDn 51 81?
?Alt-H 23 35?Alt-W 11 17?Alt-- 82 130?PgUp 49 73?
?Alt-I 17 23?Alt-X 2D 45?Alt-= 83 131? ?
?Alt-J 24 36?Alt-Y 15 21? ?^left 73 115?
?Alt-K 25 37?Alt-Z 2C 44?NUL 03 3?^right 74 116?
?Alt-L 26 38? ?Shift-Tab 0F 15?^End 75 117?
?Alt-M 32 50?Alt-0 81 129?Ins 52 82?^Home 77 119?
?Alt-N 31 49?Alt-1 78 120?Del 53 83?^PgDn 76 118?
?Alt-O 18 24?Alt-2 79 121?^PrtSc 72 114?^PgUp 84 132?
?????????????????????????????????????????????????????????????????
????????????????????????????????????????????????
? 101-key Keyboard Extensions Supported by BIOS ?
???????????????????????????????????????????????????????????????
?Key Hex Dec?Key Hex Dec?Key Hex Dec?
???????????????????????????????????????????????????????????????
?F11 85 133?Alt-Bksp 0E 14?Alt - K / A4 164?
?F12 86 134?Alt-Enter 1C 28?Alt - K * 37 55?
?Shft-F11 87 135?Alt-Esc 01 1?Alt - K - 4A 74?
?Shft-F12 88 136?Alt-Tab A5 165?Alt - K + 4E 78?
?Ctrl-F11 89 137?Ctrl-Tab 94 148?Alt - K Enter A6 166?
?Ctrl-F12 8A 138? ? ?
?Alt-F11 8B 139?Alt-up 98 152?Ctrl- K / 95 149?
?Alt-F12 8C 140?Alt-down A0 160?Ctrl- K * 96 150?
?Alt-[ 1A 26?Alt-left 9B 155?Ctrl- K - 8E 142?
?Alt-] 1B 27?Alt-right 9D 157?Ctrl- K + 90 144?
?Alt-; 27 39? ? ?
?Alt-' 28 40?Alt-Delete A3 163?Ctrl- K Up [8] 8D 141?
?Alt-` 29 41?Alt-End 9F 159?Ctrl- K Cn [5] 8F 143?
?Alt-\ 2B 43?Alt-Home 97 151?Ctrl- K Dw [2] 91 145?
?Alt-, 33 51?Alt-Insert A2 162?Ctrl- K Ins[0] 92 146?
?Alt-. 34 52?Alt-PageUp 99 153?Ctrl- K Del[.] 93 147?
?Alt-/ 35 53?Alt-PageDown A1 161? ?
???????????????????????????????????????????????????????????????
K indicates a key on the numeric keypad (when not in NumLock mode)
1.2. Special Functions
??????????????????????
There are a few functions and interrupts invoked by int 9:
int 5 - Print Screen Handler
int 15h
fns 4fh - Check Scancode
(See int 9)
85h - System Request
Normally IRET
int 23h - Ctrl-Break handler
Feel free to revector any of them.
2. DOS Interfacing
??????????????????
One of the ways to use the keyboard is to let DOS handle it.
Pro:
- The keyboard lay-out is unimportant
- You can even do strings
- The user doesn't actually have to type
Contra:
- You don't know if you are actually accessing the keyboard (like
in "Really format drive C: ? Y/N" :-)
- The functions are quite slow
2.1. Functions
??????????????
DOS provides a set of 7 functions to handle the keyboard:
01h Keyboard Input
06h Console I/O
07h No Echo Unfiltered Input
08h No Echo Filtered Input
0Ah Buffered Input
0Bh Input Status
0Ch Clear Keyboard Buffer & Input
They all expect the keyboard to be file handle 0. If you want to let a
program think you are typing something, you can replace this handle
with a file containing the keystrokes it must read. This is what
happens when you 'pipe' something in DOS. (Don't forget to change the
handle back to the old one!)
This also means you can use:
3Fh Read bytes from handle
Fn 01h: Keyboard Input
----------------------
Expects: AH 01h
Returns: AL Character fetched from the Standard Input
Description: Reads (waits for) a character from the Standard Input
Device. Echoes that character to the Standard Output
Device. If Ctrl-Break is detected, INT 23h is executed.
Notes: Extended ASCII keystrokes (ie, F1-F12, PgUp, cursor, etc)
will require two calls to this function. The first call
will return AL=0. The second will return AL with the
extended ASCII code.
Fn 06h: Console I/O
-------------------
Expects: AH 06h
DL 0 to 0FEh Character to send to the Standard Output
0FFh Request for input from the Standard Input
Returns: ZF Clear (NZ) if character is ready \ on input requests
AL Character read, if ZF is clear / (when DL=0FFh)
Description: If DL is 0FFh, this performs a "no wait" console input,
returning the Zero Flag (ZF) set (ZR) if there is no
character ready. If a character is ready, returns ZF
cleared (NZ) with the character that was read in AL.
If DL is anything but 0FFh, DL is sent to the Standard
Output.
Notes: Does not check for Ctrl-Break. Call twice for Extended
ASCII.
Fn 07h: No Echo Unfiltered Console Input
----------------------------------------
Expects: AH 07h
Returns: AL Character fetched from the Standard Input
Description: Reads (waits for) a character from the Standard Input
Device, returning that character in AL.
Unfiltered: Does not detect Ctrl-Break, backspace, etc.
Notes: Call twice for Extended ASCII character input.
Use Fn 0Bh to check status (if you don't want to wait for
a key).
Fn 08h: No Echo Console Input
-----------------------------
Expects: AH 08h
Returns: AL Character fetched from the Standard Input
Description: Reads (waits for) a character from the Standard Input
Device, returning that character in AL.
If Ctrl-Break is detected, INT 23h is executed.
Notes: Call twice for Extended ASCII character input.
Fn 0Ah: Buffered String Input
-----------------------------
Expects: AH 0Ah
DS:DX Address of an input buffer (see below)
Returns: Buffer contains input terminated with CR (ASCII 13h)
Description: On entry, the buffer at DS:DX must be set up as:
?????????????????????????? ? ?
?max? ? ? ? ? ? ? ? max is maximum acceptable
????????????????????????? ? ? input (range: 1 to 254)
On exit, the buffer is filled:
?????????????????????????? ? ? len is actual length of
?max?len? T E X T 0Dh input, less the termina-
????????????????????????? ? ? ting CR (eg, 4).
Characters are read from the Standard Input up to a CR
(ASCII 13) or up to the value of max-1. If max-1 is
reached, the console bell rings (beeps) for each character
until Enter (CR) is read.
The second byte of the buffer is filled with the actual
length of the input, less the terminating CR. The final
character in the buffer is always CR (which is not counted
in the length byte).
The characters in the buffer (including the len) before
the call are used as a "template" and the DOS editing keys
are in effect: [Esc] displays "\" and restarts the edit,
[F3] displays to the end of the template, [F5] displays
"@" and stores the current line as the template, etc.
Most Extended ASCII keystrokes are ignored.
If Ctrl-Break is detected, INT 23h is executed and the
buffer is left unchanged.
Fn 0Bh: Check Input Status
--------------------------
Expects: AH 0Bh
Returns: AL 0FFh if a character is available from the Standard Input
0 if no character is available
Description: Checks the status of the Standard Input.
If Ctrl-Break is detected, INT 23h is executed.
Notes: Use before Fns 01h, 07h and 08h to avoid having DOS wait
for a key.
This is a simple, non-destructive way to check for
Ctrl-Break during long calculations or other processing
that does not normally look for input. It lets the user
abort from such a sequence.
Fn 0Ch: Clear & Input
---------------------
Expects: AH 0Ch
AL DOS input function number (01h, 06h, 07h, 08h, or 0Ah)
Returns: none
Description: Clears the Standard Input type-ahead buffer then invokes
the DOS input function specified by AL. This forces the
system to wait for a character to be typed.
These values are allowed for AL:
01h Keyboard Input
06h Console I/O
07h No Echo Unfiltered Input
08h No Echo Filtered Input
0Ah Buffered Input
In addition to these functions, it is also possible to read a selected
amount of characters from the keyboard, using DOS's File Handle
functions, as the Keyboard, aka Standard Input, has a pre-set handle of
0000h:
Fn 3Fh: Read from keyboard via Handle
-------------------------------------
Expects: AH 3Fh
BX 0000h - Handle for Standard Input (Keyboard)
DS:DX Address of buffer to receive data
CX Number of bytes to read
Returns: AX Error code if CF is set to CY
AX Number of bytes actually read
Description: CX bytes of data are read from the keyboard. The data is
placed into the caller's buffer pointed to by DS:DX.
Notes: It is handy to use this function for reading default
handles such as the Standard I/O handles, instead of the
buffered input or character-by-character input functions.
When you read from a device, AX returns the length of the
line up to and including the termination CR (ASCII 13h).
3. BIOS Interfacing
???????????????????
Pro:
- You get to know all the statusses and such
- It's a tad bit faster than DOS
- You can only read the keyboard
- It's easier than the really hardcore low level, and the keys
are translated
Contra:
- It is still to slow for games or demos
- You don't have bulk access, like strings
The BIOS has 3 different ways of reading (parts of) the keyboard:
- functions
- keyboard flags
- keyboard buffer
This part describes all of them.
3.1. Functions
??????????????
These functions can be accessed through int 16h.
Fn 00h: Read (wait for) next keystroke
--------------------------------------
Expects: AH 0
Returns: AL ASCII character (if AL=0, AH is an Extended ASCII key-
stroke)
AH Scan Code or Extended ASCII keystroke
Fn 01h: Check if a keystroke is ready (and preview it if so)
------------------------------------------------------------
Expects: AH 1
Returns: ZF ZR or 1 if no key is ready
ZF NZ or 0 if a key is ready.
AX is set as for Fn 00h (but the keystroke has not been
removed from the queue).
Fn 02h: Read the shift-key status
---------------------------------
Expects: AH 2
Returns: AL shift key and 'lock' status as in 83-keyboard flags
Description: Determine which shift keys are currently being pressed and
whether the keyboard is in NumLock state, etc.
Fn 03h Set keyboard typeamatic rate and delay. (11/15/85 BIOS)
--------------------------------------------------------------
Expects: AH 3
AL 05h (eg, AX = 0305h)
BL Typeamatic Rate
0: 30 keys/sec 10: 10
1: 26.7 13: 9
2: 24 16: 7.5
4: 20 20: 5
8: 15 31: 2
BH Delay: 0=250ms 1=500ms 2=750ms 3=1 second)
Returns: none
Description: when a key is pressed, the keyboard will wait during Delay
before it starts repeating at Typematic Rate.
Fn 05h Place a keystroke into the keyboard buffer. (11/15/85 BIOS)
------------------------------------------------------------------
Expects: AH 5
CL ASCII character.
CH Scan Code byte (or 0 if you don't care)
Returns: AL Status: 0=success; 1=buffer full
Fn 10h Read (wait for) a keystroke; 101-keyboard only (11/15/85 BIOS)
---------------------------------------------------------------------
Expects: AH 10h
Returns: AL ASCII character (if AL=0, AH is an Extended ASCII key-
stroke)
AH Scan Code or Extended ASCII keystroke
Fn 11h Preview keystroke; same as 01; 101-keyboard only (11/15/85 BIOS)
-----------------------------------------------------------------------
Expects: AH 11h
Returns: ZF ZR or 1 if no key is ready
ZF NZ or 0 if a key is ready.
AX set as for Fn 10 but keystroke is still in the buffer.
12h Read shift-key status; same as 02; 101-keyboard only (11/15/85 BIOS)
------------------------------------------------------------------------
Expects: AH 12H
Returns: AL shift key and 'lock' status as in 101-keyboard flags
3.2. Keyboard Flags
???????????????????
The keyboard flags are found in the BIOS Data Area: segment 40h.
17h: 83-keyboard flags 0=Off, 1=On
---------------------------------------
bit 0: Right shift
1: Left shift
2: Ctrl, either side
3: Alt, either side
4: Scroll Lock
5: Num Lock
6: Caps Lock
7: Insert state
Do NOT just change one of these and then hope the keyboard follows. The
LEDs will definitely get out of sync.
18h: 101-keyboard flags 0=Off, 1=On
---------------------------------------
bit 0? : Left ctrl
1??At keyb. only : Left Alt
2? : Sys Req
3: Pause state
4: Scroll Lock ?
5: Num Lock ??Being pressed
6: Caps Lock ?
7: Insert ?
Do NOT just change one of these and then hope the keyboard follows. The
LEDs will definitely get out of sync.
19h: Pseudokey value
--------------------
This is the accumulating value of the key being made with Alt+numeric
keypad. Normally 0
71h: Ctrl-break flag 0=Off, 1=On
---------------------------------------
bit 7: Ctrl-Break was pressed. Never gets reset, unless you do.
96h: AT only - keyboard ? 0=Off, 1=On
---------------------------------------
bit 4: 101/102 keyboard is attached
97h: AT only - lock LEDs 0=Off, 1=On
---------------------------------------
bit 0: ScrollLock ?
1: NumLock ?? keyboard LED is turned on
2: CapsLock ?
Do NOT just change one of these and then hope the keyboard follows.
The LEDs will definitely get out of sync.
3.3. Keyboard Buffer
????????????????????
The keyboard buffer is a circular data area. This means that when a
pointer in the buffer gets one larger than the buffer, it is wrapped
around to the beginning.
The keyboard buffer is fed by int 9 and function 5 of int 16h. It is
found at the BIOS data segment, 40h. It is pointed to by 4 variables in
the BDA: The head (1ah), the tail (1ch), the Beginning (80h) and the
End (82h). They are all words, pointing at locations in the BDA.
The latter two are only available on ATs and PSs. They are used to
enlarge the keyboard buffer by mapping it to another spot in the BIOS
data area. Normally, that spot is 32 bytes long starting from 1eh.
The head is the pointer to the next word. The tail is the pointer to
the next available word. Each code is two bytes, the scan code and the
ASCII value.
The buffer is empty if the Head = the Tail and it is full if the Tail
is two smaller than the Head, both counted circularly. This means that
the storage space equals (length buffer/2)-1.
4. Low-Level Interfacing
????????????????????????
Pro:
- Fast
- Complete control
Contra:
- Hard to code
- Totally NO functions at all. It's Handyman work here...
The interfacing is split in two items:
- Just changing something, such as the LED's
- Reading out codes: int 9
4.1. Interfacing And Configuring
????????????????????????????????
The computer and the AT or MF II interface through I/O ports 60h and
64h, controlled by a programmable Intel 8042 (old ATs), 8741 or 8742
(newer, allow two input devices (like the PS/2 mouse)) microprocessor
or compatible, which allows typematic rate programming, LEDs lighting
and some other stuff. It also has a +-20 byte output buffer for smooth
operation and long scancodes.
The old XT keyboard has a 8048, which is in essence just a very
primitive one-way serial interface, so all used is port 61h, to disable
and reenable the keyboard on every scancode.
Port 60h: Input & output
------------------------
Read: Scancodes and keyboarddata
--------------------------------
This port gives the following output codes:
00h: Keyboard error, too many keys are being pressed at once
aah: Basic Assurance Test (BAT) end
abh 41h: The result of requesting keyboard ID on a MF II keyboard
eeh: The result of the echo command
fah: ACK(noledge). Sent by every command, except eeh and feh
fch: BAT failed
feh: Resend your data please
ffh: Keyboard error
All the rest are make (press) and break (release) codes of the keys.
Write: Command data
-------------------
This is the place where command data has to be sent. If the command
consists of two bytes, you must wait until the outputbuffer is sent to
the keyboard. Check on it via bit 1 of port 64h. When you send a
command, the outputbuffer is cleared, so pending results may not come.
During transmission of a two-byte command, the keyboard stops scanning.
When you send something out of range or so, the keyboard will react
with feh (resend). All commands, except echo (eeh) and resend (feh)
result in ACK (fah) to be sent.
Commands:
edh: Set keyboard LEDs
Send a second byte with:
bit 0 = Scroll Lock 0=Off 1=On
1 = Num Lock
2 = Caps Lock
rest = 0
Do make an effort to keep the BIOS keyboard flags in sync.
eeh: Great fun. Send it, and get 0eeh right back! :-]
(Diagnostics)
f0h: Select scancode set.
0: return current set number: 1:'C', 2:'A', 3:'?'
1: set scancode set no 1
2: set scancode set no 2 -> standard
3: set scancode set no 3
f2h: Identify keyboard
XT: nothing (that is, time-out error :-) (see port 64h)
AT: ACK
MF II: ACK abh 41h
f3h: Typematic rate programming
Send a second byte with:
bit 0 -> 4: rate. Timings:
0: 30 keys/sec 10: 10
1: 26.7 13: 9
2: 24 16: 7.5
4: 20 20: 5
8: 15 31: 2
bit 5 & 6: pause before repeat:
0: 250 ms
1: 500
2: 750
4: 1000
bit 7: Always 0
The next three are doubtfull, since one of my sources say they don't
exist and another says they do. I leave it up to you :)
f4h: Enable keyboard. It clears its buffer and starts scanning.
f5h: Reset keyboard, disable scanning
f6h: Reset keyboard, enable scanning
feh: Resend last transmission. I really don't know what it does, since
it sends something incomprehesible.
ffh: Internal diagnostics: Sends aah if successfull. Warning! The
keyboard reacts with ACK and then you have to set the data and
clock pins high, DURING AT LEAST 500 SECONDS!. Do this via the
outputport (see 64h). After that, the BAT (Basic Assurance Test)
starts. This sends aah on success and fch on failure.
Example: Set the keyboard LEDs
start:
in al, 64h \It would be good
and al, 02h ;Test if command buffer is empty |to put this in a
jnz start /macro...
mov al, edh
out 60h, al ;Write outputport
wait:
in al, 64h
and al, 02h ;Test if command came through
jnz wait
mov al, 0111b
out 60h, al ;Set all LED's to ON.
Port 61h
--------
This port is used to acknoledge the receival of a scancode, by
disabling the keyboard and immediately reenabling it. This also means
that you can read a scancode as many times as you like, until you
acknoledge the receival.
bit 0 -> 5: Nothing to do with keyboard, but with the Programmable
Peripheral Interface (PPI) -> save them!
bit 6: Hold keyboard clock low -> Keyboard can't send any data.
bit 7: 0=Enable keyboard; 1=Disable keyboard
Example:
in al, 61h
mov ah, al ;Save keyboard status
or al, 80h ;Disable
out 61h, al
mov al, ah ;Enable (If it was disabled at first, you wouldn't
out 61h, al ; be doing this anyway :-)
Port 64h: Interface: data and control
-------------------------------------
Read: Statusport
----------------
bit 0: 1: Keyboard data is in buffer
0: Output buffer empty -> use it to check for results
1: 1: User data is in buffer
0: Command buffer is empty -> time to send a command
2: 1: Selftest successful
0: Reset (?)
3: 1: 64h was last accessed port
0: 60h was last accessed port
4: 1: Keyboard enabled
0: Keyboard locked
5: PS/2: Mouse interface
6: 1: Time-out error occurred: Keyboard or PS/2 mouse didn't
react. Use the Resend command to retry fetching the data
byte. This could happen when trying to get a XT keyboard
to do something :).
7: 1: Last transmission had a parity error
Write: Control register
-----------------------
This is the control room of the keyboard interface. If additional data
is required, send it to port 60h after writing the command to 64h.
Also, check 61h bit 2 before sending anything.
Commands:
aah: Keyboard self test. Sends 55h if successfull.
abh: Test interface. Sends:
00h: No error
01h: Clock low
02h: Clock high
03h: Data low
04h: Data high
ffh: Total Error
adh: Deactivate keyboard
aeh: Activate keyboard
c0h: Read inputport. This is some highly specialized stuff and I wonder
why I am typing this. Ok. The inputport is that what the keyboard
is sending and some more. Layout:
bit 0: Keyboard data in pin
1: PS/2 mouse in pin
2->5: reserved
6: Wether you have a color or mono screen
7: 1: Keyboard not locked
0: Keyboard locked
When you issue this command, the inputport is put on the
outputbuffer, so you have the great priviledge of reading it at
port 60h.
c1h: Puts the low nibble of the input port over bits 4-7 of the
statusport, so you can read them out continuously. This lasts
until bit 2 of the statusport gets set, meaning you are sending
data to the keyboard.
c2h: Ditto, but it puts the high nibble over bits 0-3 of the
statusport. Lifespan is the same.
d0h: Puts the outputport on the buffer. Layout:
bit 0: 1: Reset processor
1: 1: A20 gate enable
2: PS/2 mouse data out
3: PS/2 mouse clock signal
4: 1: Output buffer full
5: 1: Output buffer PS/2 mouse full
6: Keyboard clock signal
7: Keyboard data out
Bit 0 and 1 are quite important for high memory and
286-extended-memory access.
d1h: Write the following data byte to the outputport
d2h: Write the following data byte to the keyboardbuffer. This is VERY
handy for TSRs that need to read codes that start with e0h. This
way, they don't have to pass through the e0h, unless they know for
sure it isn't their code, which results in correct functioning
shift keys etc. At least, if it does what I think it
does... [UNTESTED]
d3h: Ditto, for PS/2 mouse.
d4h: Write byte to PS/2 mouse.
e0h: Reads the keyboards testinputs, T0 and T1. T0 goes to bit 0 and T1
to bit 1 of the byte that is put on the outputbuffer.
fxh: I think it sends x to the low nibble of the output port. It does
reset my computer when I send feh, but that doesn't mean anything
:-). The official explanation says that it keeps the corresponding
bits in the output port low for 6ms...
Example: Send something to the outputport
start:
in al, 64h \It would be good
and al, 02h ;Test if command buffer is empty|to put this in a
jnz start /macro...
mov al, d1h
out 64h, al ;Write outputport
wait:
in al, 64h
and al, 02h ;Test if command came through
jnz wait
mov al, 01h
out 60h, al
4.2. Lay-Out
????????????
The keyboard first consisted of 83 keys, which is now known as the XT
keyboard. Then came along the AT-keyboard, which has 84 keys, a
slightly different layout and an extra SysReq key. The next keyboard is
the MF II keyboard. This one has 101 or 102 keys, and this is the one
this section will be babbling about.
The keycaps change, but the most popular settings are QWERTY and
AZERTY. Also popular is the Dvorak lay-out, made by what's-his-name
Dvorak, who made the lay-out so that both hands did not have to move
that much, resulting in fast (up to double) typing speed. This is it,
should you be interested (slight modifications by me, because it
actually requires a 12x4 keyboard):
101 - key 102 - key
~ ! @ # $ % ^ & * ( ) [ + ? ! @ # $ % ^ & * ( ) [ +
` 1 2 3 4 5 6 7 8 9 0 ] = ? 1 2 3 4 5 6 7 8 9 0 ] =
" , . P Y F G C R L ? { | " , . P Y F G C R L ? {
' , . p y f g c r l / } \ ' , . p y f g c r l / }
A O E U I D H T N S _ < A O E U I D H T N S _ ~
a o e u i d h t n s - > a o e u i d h t n s - `
: Q J K X B M W V Z > : Q J K X B M W V Z
; q j k x b m w v z < ; q j k x b m w v z
The key lay-out is as follows: (The numbers are internal to the
keyboard)
US-English Keyboard: 101 keys
-----------------------------
????????????????????????????????????????????????
?10??12?13?14?15??16?17?18?19??20?21?22?23??24?25?26? 0 when pressed, 1 when released.
Ctrl-Alt-Del:
Reboot. Here's a sample of how to reboot:
mov ah,0Dh ; Disk Reset
int 21h ; causes SmartDrv 4.x to write cache
mov ax, 40h ; set up segment addressing
mov ds,ax
or byte ptr ds:[17h],0Ch ; equivalent of pressing CTRL+ALT
mov ax,4F53h ; Issue a "DEL" (53h = DEL scan code)
int 15h ; EMM386 sees this & shuts down
mov word ptr ds:[72h],1234h ; Set REBOOT flag to Warm-Boot (0=cold)
db 0EAh,0h,0h,0FFh,0FFh ; JMP FFFF:0000
Of course, the int 15h call should already have been done by the
handler. It is also used by other caches to flush.
Shift-numkeypad:
Temporarily reverse the NumLock state, e.g. 8 becomes arrow up and
vice versa.
Alt+numkeypad:
Make the pseudokey in BDA byte 19h until the alt is released, then
put it in the keyboard buffer. How? Well, everytime an extra number
comes in, multiply BDA:19h with 10 and add the new number.
Alt release:
See above. Just making sure it is implemented ;-)
Ctrl+a->z:
Send bytes 1 through 27
Foreign keyboards:
Some keys are accents, to be placed on the next key.
Right alt:
Some keys have three keys on it. To access them, the right alt is
pressed. So remember to send the right ASCII code...
NumLock:
Switch numkeypad on/off and light/switch off LED
CapsLock:
Translate normal letters to caps or vice versa and light/switch off
LED. A nice touch would be to have a distinction between CapsLock
and Ctrl-CapsLock. The former would shift alfabetic
keys only and the latter all keys...
ScrollLock:
Light/sw. off LED
Int 9 also has to adjust the BDA flags and keyboard buffer. In
addition, the driver should warn when the keyboard buffer is full.
5. Tech Stuff
?????????????
Interface:
Bidirectional, serial synchronous. The keyboard communicates via
clock and data line with the system. The data comes in 11 bit
packets, namely start-data-parity-stop. Parity is uneven.
=1 8bit 1bit =0
Also, see further.
Data Format:
Data transfer to and from the keyboard in IBM-compatible format:
AT-, PS/2-mode: Idle state - "Data & Clock" high.
PC mode: Idle state - "Data" low, "Clock" high.
Data Output:
Open drain.
Keyboard Sequence:
Alpha-N-key-rollover.
Automatic repeat function:
All keys have auto repeat. Delay and repeat sequence can be
modified through the system, but is fixed for PC-mode. (10Hz after
500ms)
Keyboard Self-diagnostic test:
After "Power-On" or upon request, the keyboard carries out a
self-diagnostic test. After positive test, the keyboard sends AAh.
Any other is a failure.
Pin assignment:
___ 1 Clock
/524\ 2 Data
|3 1|? 3 Not used
\_?_/ ?chassis gnd 4 Gnd
- 5 +5V (This is the place to tap from :-)
PS/2 adaptor: 1 Data
_ _ 2 Not used
/5U6\ 3 Gnd
|3 4|? 4 +5V
\1_2/ ?chassis gnd 5 Clock
- 6 Not used
The PC-XT keyboard communication protocol
-----------------------------------------
Below is a drawing of the timing of the data, send to the PC. The upper
line shows the clock line, the lower the data line. The text above
indicates the position of the start, data and stop bits (clocked on the
negative edge of the clock line).
Start 1 2 3 4 5 6 7 8 Stop
? ? ? ? ? ? ? ? ? ?
??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ????
clk???? ???? ???? ???? ???? ???? ???? ???? ???? ????
??????????????????????????????????????????????????????? ??
dta ???????????????????????????????????????????????????????
The communication abides to the following rules:
- On power up or reset, the PC pulls the clock line (normally high)
low for at least 20 ms. When it is released (goes high again),
the keyboard should send the code 0AAh to the PC to indicate its
existance.
- The data is clocked in on the negative edge of the clock signal.
The clock line must normally be high, the data line can be
anything between transmissions. The clock line is delayed two PC
clock cycles in the PC, so data changes and the negative clock
edge may take place at the same time. It is safer, however, to
build in a bigger delay.
- A transmission starts with a start bit (high). Then follow eight
data bits, of witch bit 7 (MSB) indicates the release of the key.
After that normally follows a stop bit (low), but that may be
left out. In fact, due to the shift register hardware inside the
PC, any number of stop bits could be send, as long as they are
low. Not 100% hardware compatibles, however, may get confused
then.
- After a transmission, the PC pulls the data line low until it is
ready processing the data. The keyboard should wait with sending
any more data until the PC releases the data line again.
A. Acknowledgments
??????????????????
This text was made by Wout Mertens, with the help of Tech Help of
Flambeaux software, the tech spex of Cherry and some texts I found.
Information on the PC-XT keyboard communication protocol and the
kbfunc.c file by Gertjan Klein (Floating somewhere in cyberspace).
Cherry is the registered trademark of Cherry Microschalter Gmbh etc.
IBM is the registered trademark of the IBM corporation
Mertens is the registered trademark of the Mertens Family ;-)
Improved copyright notice, thanks & greetings to:
Emil Gilliam (Floating in cyberspace as well)
Kip Cooley at the Diamond Bar BBS (909) 923-1031 (1:218/101).
Ian Remmler at the DownTown BBS (210) 625-4479 (1:387/1001).
B. How To Contact Me
????????????????????
Please let me know if something is inaccurate or missing etc. Also, I
would like some feedback on the quality and usability of this text.
(Keeps me writing...) If you think this text is very usefull, you can
always send me a nice postcard from where you live to thank me... I will
then try to notify you when a new version arrives.
I am usually reachable through the Fido 80XXX echo, but you can also
reach me at the following addresses:
Fido 2:292/805.1
SBC 14:1900/457
DGI 68:320/1.3
CDN 94:810/1104
CIN 112:913/101.4
SnailMail: Wout Mertens
Jozef de Bomstr 62
2018 Antwerp
Belgium - Europe
C. The Answer To Life, The Universe And All The Rest
????????????????????????????????????????????????????
42.
PS: Could anyone tell me the Question?
(With thanks to Douglas Adams :-)
D. History
??????????
20 feb 94: release of v1.0
5 apr 94: changed info on rebooting in int 9
added info about XT protocol, by Gertjan Klein
added C program to interface with keyboard, by Gertjan Klein
removed a bug in the copyright: Emil Gilliam was not to be
held liable :-):-):-)
removed some general typing errors
9 apr 94: removed bug in keyboard buffer info: Head and Tail do not
point to a location relative to Beginning, but instead
directly to the keyboardbuffer
23 may 94: v1.1
