VT82C686B

Manufacturer Part NumberVT82C686B
ManufacturerETC-unknow
VT82C686B datasheet
 


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Keyboard Controller Registers
The keyboard controller handles the keyboard and mouse
interfaces. Two ports are used: port 60 and port 64. Reads
from port 64 return a status byte. Writes to port 64h are
command codes (see command code list following the register
descriptions). Input and output data is transferred via port 60.
A “Control” register is also available. It is accessable by
writing commands 20h / 60h to the command port (port 64h);
The control byte is written by first sending 60h to the
command port, then sending the control byte value.
control register may be read by sending a command of 20h to
port 64h, waiting for “Output Buffer Full” status = 1, then
reading the control byte value from port 60h.
Traditional (non-integrated) keyboard controllers have an
“Input Port” and an “Output Port” with specific pins dedicated
to certain functions and other pins available for
purpose I/O. Specific commands are provided to set these pins
high and low. All outputs are “open-collector” so to allow
input on one of these pins, the output value for that pin would
be set high (non-driving) and the desired input value read on
the input port. These ports are defined as follows:
Bit
Input Port
0
P10 - Keyboard Data In
1
P11 - Mouse Data In
2
P12 - Turbo Pin (PS/2 mode only)
3
P13 - user-defined
4
P14 - user-defined
5
P15 - user-defined
6
P16 - user-defined
7
P17 - undefined
Bit
Output Port
0
P20 - SYSRST (1=execute reset)
1
P21 - GATEA20 (1=A20 enabled)
2
P22 - Mouse Data Out
3
P23 - Mouse Clock Out
4
P24 - Keyboard OBF Interrupt (IRQ1) –
5
P25 - Mouse OBF Interrupt (IRQ 12) –
6
P26 - Keyboard Clock Out
7
P27 - Keyboard Data Out
Bit
Test Port
0
T0 - Keyboard Clock In
1
T1 - Mouse Clock In
Note: Command code C0h transfers input port data to the
output buffer. Command code D0h copies output port values
to the output buffer. Command code E0h transfers test input
port data to the output buffer.
Port 60 - Keyboard Controller Input Buffer ................. WO
Only write to port 60h if port 64h bit-1 = 0 (1=full).
Port 60 - Keyboard Controller Output Buffer ................ RO
Only read from port 60h if port 64h bit-0 = 1 (0=empty).
Revision 1.71 June 9, 2000
Port 64 - Keyboard / Mouse Status .................................. RO
7
Parity Error
6
General Receive / Transmit Timeout
5
Mouse Output Buffer Full
The
4
Keylock Status
3
Command / Data
general
2
System Flag
1
Input Buffer Full
Lo Code Hi Code
0
Keyboard Output Buffer Full
B0
B8
B1
B9
B2
BA
B3
BB
KBC Control Register .......... (R/W via Commands 20h/60h)
B6
BE
7
Reserved
B7
BF
6
PC Compatibility
Lo Code Hi Code
5
Mouse Disable
B4
BC
B5
BD
4
Keyboard Disable
3
Reserved
Lo Code Hi Code
System Flag ................................................default=0
2
This bit may be read back as status register bit-2
1
Mouse Interrupt Enable
0
Keyboard Interrupt Enable
-40-
VT82C686B
0
No parity error (odd parity received)..... default
1
Even parity occurred on last byte received
from keyboard / mouse
0
No error ................................................. default
1
Error
0
Mouse output buffer empty.................... default
1
Mouse output buffer holds mouse data
0
Locked
1
Free
0
Last write was data write ....................... default
1
Last write was command write
0
Power-On Default .................................. default
1
Self Test Successful
0
Input Buffer Empty................................ default
1
Input Buffer Full
0
Keyboard Output Buffer Empty............. default
1
Keyboard Output Buffer Full
........................................always reads 0
0
Disable scan conversion
1
Convert scan codes to PC format; convert 2-
byte break sequences to 1-byte PC-compatible
break codes ............................................ default
0
Enable Mouse Interface ......................... default
1
Disable Mouse Interface
0
Enable Keyboard Interface .................... default
1
Disable Keyboard Interface
........................................always reads 0
0
Disable mouse interrupts ....................... default
1
Generate interrupt on IRQ12 when mouse data
comes in output bufer
0
Disable Keyboard Interrupts.................. default
1
Generate interrupt on IRQ1 when output buffer
has been written.
Register Descriptions - Legacy I/O Ports