ADB.txt

   1 ADB Protocol
   2 ============
   3
   4 Resources
   5 ---------
   6 Apple IIgs Hardware Reference Second Edition [p80(Chapter6 p121)]
   7     ftp://ftp.apple.asimov.net/pub/apple_II/documentation/Apple%20IIgs%20Hardware%20Reference.pdf
   8 ADB Keycode
   9     http://72.0.193.250/Documentation/macppc/adbkeycodes/
  10     http://m0115.web.fc2.com/m0115.jpg
  11 ADB Signaling
  12     http://kbdbabel.sourceforge.net/doc/kbd_signaling_pcxt_ps2_adb.pdf
  13 ADB Overview & History
  14     http://en.wikipedia.org/wiki/Apple_Desktop_Bus
  15 Microchip Application Note: ADB device(with code for PIC16C)
  16     http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011062
  17 AVR ATtiny2131 ADB to PS/2 converter(Japanese)
  18     http://hp.vector.co.jp/authors/VA000177/html/KeyBoardA5DEA5CBA5A2II.html
  19
  20
  21 Pinouts
  22 -------
  23     Female socket from the front
  24
  25       4o  o3
  26      2o    o1
  27         ==
  28
  29     1: Data
  30     2: Power SW(low when press Power key)
  31     3: Vcc(5V)
  32     4: GND
  33
  34
  35 Commands
  36 --------
  37     ADB command is 1byte and consists of 4bit-address, 2bit-command
  38     type and 2bit-register. The commands are always sent by Host.
  39
  40     Command format:
  41     7 6 5 4 3 2 1 0
  42     | | | |------------ address
  43             | |-------- command type
  44                 | |---- register
  45
  46     bits                commands
  47     ------------------------------------------------------
  48     - - - - 0 0 0 0     Send Request(reset all devices)
  49     A A A A 0 0 0 1     Flush(reset a device)
  50     - - - - 0 0 1 0     Reserved
  51     - - - - 0 0 1 1     Reserved
  52     - - - - 0 1 - -     Reserved
  53     A A A A 1 0 R R     Listen(write to a device)
  54     A A A A 1 1 R R     Talk(read from a device)
  55
  56     The command to read keycodes from keyboard is 0x2C which
  57     consist of keyboard address 2 and Talk against register 0.
  58
  59     Address:
  60     2:  keyboard
  61     3:  mice
  62
  63     Registers:
  64     0: application(keyobard/mice use to store its data.)
  65     1: application
  66     2: application
  67     3: status and command
  68
  69
  70 Communication
  71 -------------
  72     This is a minimum information for keyboard communication.
  73     See "Resources" for detail.
  74
  75     Signaling:
  76
  77     ~~~~____________~~||||||||||||__~~~~~_~~|||||||||||||||__~~~~
  78
  79         |800us     |  |7 Command 0|  |   |  |15-64  Data  0|Stopbit(0)
  80         +Attention |              |  |   +Startbit(1)
  81                    +Startbit(1)   |  +Tlt(140-260us)
  82                                   +stopbit(0)
  83
  84     Bit cells:
  85
  86     bit0: ______~~~
  87           65    :35us
  88
  89     bit1: ___~~~~~~
  90           35 :65us
  91
  92     bit0 low time: 60-70% of bit cell(42-91us)
  93     bit1 low time: 30-40% of bit cell(21-52us)
  94     bit cell time: 70-130us
  95     [from Apple IIgs Hardware Reference Second Edition]
  96
  97     Criterion for bit0/1:
  98     After 55us if line is low/high then bit is 0/1.
  99
 100     Attention & start bit:
 101     Host asserts low in 560-1040us then places start bit(1).
 102
 103     Tlt(Stop to Start):
 104     Bus stays high in 140-260us then device places start bit(1).
 105
 106     Global reset:
 107     Host asserts low in 2.8-5.2ms. All devices are forced to reset.
 108
 109     Send request from device(Srq):
 110     Device can request to send at commad(Global only?) stop bit.
 111     keep low for 300us to request.
 112
 113
 114 Keyboard data(register0)
 115     This 16bit data can contains 2 keycodes and 2 released flags.
 116     First keycode is palced in upper nibble. When one keyocode is sent,
 117     lower nibble is 0xFF.
 118     Release flag is 1 when key is released.
 119
 120     15 14 . . . . . 8 7 6 . . . . . 0
 121     |  |keycode1      | |keycode2
 122     |released(1)      |released(1)
 123
 124     Keycodes:
 125     Scancode consists of 7bit keycode and 1bit release flag.
 126     Device can send two keycodes at once. If just one keycode is sent
 127     keycode1 contains it and keyocode2 is 0xFF.
 128
 129     Power switch:
 130     You can read the state from PSW line(active low) however
 131     the switch has a special scancode 0x7F7F, so you can
 132     also read from Data line. It uses 0xFFFF for release scancode.
 133
 134 END_OF_ADB