"8042" PS/2 Controller: Difference between revisions
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The PS/2 Controller (often called a “Keyboard controller”) is located on the mainboard. In the early days the controller was a single chip ('''Intel 8042'''). As of today it is part of the [[Advanced Integrated Peripheral]].▼
▲The PS/2 Controller (often called a “Keyboard controller”) is located on the mainboard. In the early days the controller was a single chip (8042). As of today it is part of the [[Advanced Integrated Peripheral]].
The name is misleading because the controller does more than controlling communication with PS/2 devices.
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* Wait for the device to send "ACK" back (0xFA)
* Wait for the device to send up to 2 bytes of reply, with a time-out to determine when it's finished (e.g. in case it only sends 1 byte)
* Send the "enable scanning" command 0xF4 to the device
A partial list of responses includes:
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{| {{wikitable}}
|-
! Bytes (Normal)
! Bytes (Translated*)
! Device Type
|-
| None
| None
|-
| 0x00
| n/a
| Standard PS/2 mouse
|-
| 0x03
| n/a
| Mouse with scroll wheel
|-
| 0x04
| n/a
| 5-button mouse
|-▼
| 0xAB, 0x41 or 0xAB, 0xC1▼
|-
| 0xAB, 0x83
▲| MF2 keyboard
| rowspan="2" | MF2 keybaord
▲|-
| 0xAB, 0xC1
| 0xAB, 0xC1
|-
| 0xAB, 0x84
| 0xAB, 0x54
| IBM ThinkPads, Spacesaver keyboards, many other "short" keyboards
|-
| rowspan="2" | 0xAB, 0x85
| rowspan="2" | 0xAB, 0x85
| NCD N-97 keyboard
|-
| 122-Key Host Connect(ed) Keyboard
|-
| 0xAB, 0x86
| 0xAB, 0x86
| 122-key keyboards
|-
| 0xAB, 0x90
| 0xAB, 0x90
| Japanese "G" keyboards
|-
| 0xAB, 0x91
| 0xAB, 0x91
| Japanese "P" keyboards
|-
| 0xAB, 0x92
| 0xAB, 0x92
| Japanese "A" keyboards
|-
| 0xAC, 0xA1
| 0xAC, 0xA1
| NCD Sun layout keyboard
|}
<nowiki>*</nowiki> Translation is not possible for the second PS/2 port
Note: If anyone sees any other responses please add to the list above!▼
Notes:
Once your PS/2 Controller driver knows what types of PS/2 devices are present, it can start suitable device drivers for those devices. Don't forget that we've left devices in a "scanning disabled" state.▼
* Translated IDs are provided in the table above for completeness, but it's arguably better to disable translation in the controller prior to pulling a device ID to avoid potential confusion.
▲Once your PS/2 Controller driver knows what types of PS/2 devices are present, it can start suitable device drivers for those devices
== Hot Plug PS/2 Devices ==
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== CPU Reset ==
To trigger a CPU Reset, regardless of what state the CPU is in, write the value 0xFE to the Output port.
<
;Wait for a empty Input Buffer
wait1:
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mov al, 0xFE
out 0x64, al
</syntaxhighlight>
==See Also==
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*[[Post:69151|PS/2 controller initialisation]]
===External Links===
* [http://web.archive.org/web/20210417040153/http://www.diakom.ru/el/elfirms/datashts/Smsc/42w11.pdf
[[Category:X86]]
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