Add doc 4704.txt and protocol comment
tmk
11 years ago
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4704 Keyboard
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=============
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Keyboard Models:
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Model 100 6019273 50-key (grid layout)
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Model 200 6019284 62-key Alpha(60% layout)
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Model 300 6019303 77-key Expanded Alpha
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Model 400 6020218 107-key Full key
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Resourse
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--------
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The IBM 4704: lots of pictures and info
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http://kishy.dyndns.org/?p=648#more-648
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Brochure:
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http://ed-thelen.org/comp-hist/IBM-ProdAnn/4700.pdf
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4704 Keyboard Protocol
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======================
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On powering up the keyboard sends keyboard id; A3h for 6019284(62-key), for example.
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After that firmware enters FC command mode and waits for parameter data from host
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so that it doesn't send any scancode until you send 'FF'(End of FC command).
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Keyboard to Host
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----------------
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Data bits are LSB first and Pairty is odd. Clock has around 60us high and 30us low part.
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____ __ __ __ __ __ __ __ __ __ ________
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Clock \____/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
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____ ____ ____ ____ ____ ____ ____ ____ ____ ____
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Data ____/ X____X____X____X____X____X____X____X____X____X________
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Start 0 1 2 3 4 5 6 7 P Stop
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Start bit: can be long as 300-350us.
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Inhibit: Pull Data line down to inhibit keyboard to send.
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Timing: Host reads bit while Clock is hi.
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Stop bit: Keyboard pulls down Data line to lo after 9th clock.
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Host to Keyboard
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----------------
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Data bits are LSB first and Pairty is odd. Clock has around 60us high and 30us low part.
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____ __ __ __ __ __ __ __ __ __ ________
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Clock \______/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/
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^ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ___
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Data ____|__/ X____X____X____X____X____X____X____X____X____X \___
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| Start 0 1 2 3 4 5 6 7 P Stop
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Request by host
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Start bit: can be long as 300-350us.
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Request: Host pulls Clock line down to request to send a command.
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Timing: After Request keyboard pull up Data and down Clock line to low for start bit.
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After request host release Clock line once Data line becomes hi.
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Host wirtes a bit while Clock is hi and Keyboard reads while low.
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Stop bit: Host releases or pulls up Data line to hi after 9th clock and waits for keybaord pull down the line to lo.
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Scancodes
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---------
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Keyboard doesn't send Break code for all keys except for Alt by default.
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6019284 62-key:
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,-----------------------------------------------------------.
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| `| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| -| =|???|BS |
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|-----------------------------------------------------------|
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|Tab | Q| W| E| R| T| Y| U| I| O| P| ￠| \| PD2|
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|-----------------------------------------------------------|
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|Ctrl | A| S| D| F| G| H| J| K| L| ;| '| {}| PD3|
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|-----------------------------------------------------------|
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|Shif| <>| Z| X| C| V| B| N| M| ,| ,| /|???|Shift |
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|-----------------------------------------------------------|
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|Reset|blk|Alt | Space |Alt |blk|Enter|
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`-----------------------------------------------------------'
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+----------+---------------------+----------+----------+
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|` 00|PD1 04|Caps 20|LShift 30|Reset 31|
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|1 18|q 05|a 21|<> 3E|Rblank 41|
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|2 19|w 06|s 22|z 32|Alt 3F|
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|3 1A|e 13|d 23|x 33|Space 40|
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|4 10|r 14|f 24|c 34|Alt 3F|
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|5 11|t 15|g 25|v 35|Lblank 42|
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|6 12|y 16|h 26|b 36|Enter 2F|
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|7 08|u 17|j 27|n 37| |
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|8 09|i 01|k 28|m 38| |
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|9 0A|o 02|l 29|, 39| |
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|0 0F|p 03|; 2A|. 3A| |
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|- 1F|￠ 1B|' 2B|/ 3B| |
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|= 0D|\ 1C|{} 2C|??? 3C| |
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|??? 0C|PD2 1D|PD3 2D|RShift 3D| |
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|BS 0E| | | | |
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+----------+---------------------+----------+----------+
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Bit7 is 'press flag' which set 1 on press and 0 on release when break code is enabled.
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NOTE: When break code is enabled the key sends scancode with setting 7th bit on press
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and without it on release. That is, '`' sends 80h on press and 00h on release.
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keyboard command
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----------------
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FF Soft Reset(0008h)
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FE Resend(00e8h)
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FD Buzzer stop?(00edh)
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FC Set Key flag(00f6h)
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FB Soft Reset(0008h)
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FA Reset(0000h)
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Keyboard response
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-----------------
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FF Not exist. [Outgoing buffer cannot have FFh(00h in fact)]
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FE Overflow(key event/receive data) at 00c5h, 0346h
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FE Memory test error at 0224h
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FD Command out of bound at 00d8h
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Key out of bound
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7E Read/Parity error in receive from host at 00bch
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Set Key flag command(FC)
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------------------------
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After 'Power on Reset' firmware enters this command mode and waits for data from host,
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so that you don't need to send 'FC' and it doesn't send any scancode until you send 'FF'.
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Data sent from host:
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bit: 7 6 ... 0
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en | |
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| `-----`--- scan code
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`------------- enable bit(0: enable repeat, 1: enable break)
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00-77 Enable repeat(78-7F: invalid scancode)
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80-F7 Enable break(F8-FF: invalid scancode)
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FE Resend(011ah) no need to use
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FF End(0114h) exits FC command mode.
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Response from keyboard:
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FD Out of bound - Invalid scancode
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Examples:
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To enable break code of all keys.
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FC 80 81 ... F7 FF
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