VT82C42 View Datasheet(PDF) - Unspecified
Part Name
Description
Manufacturer
VT82C42 Datasheet PDF : 13 Pages
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VIA Technologies, Inc.
VT82C42
4. Register
Table 1. Status register: read only (with A0 = 1, CS# = 0, RD# = 0, WR# = 1)
Bit0 : OBF
1 means output buffer is full, 0 means output buffer is empty.
Bit1 : IBF
1 means input buffer is full, 0 means input buffer is empty.
Bit2 : system flag
0 after power on
Bit3 : command/Data
1 means last write is command write. 0 means last write is data write.
Bit4 : keylock status
To represent the inhibition of keyboard. 0 means keyboard is inhibited. 1
means keyboard is not inhibited.
Bit5 : transmit time-
Act as transmit time-out on AT mode. 1 means error happens. Act as Mouse
out/mouse OBF
OBF on PS2 mode. 1 means mouse output buffer full.
Bit6 : receive time-
Act as receive time-out on AT mode. 1 means error happens. Act as general
out/general time-out
(receive/transmit) time-out on PS2 mode.
Bit7 : parity error
1 means even parity has occurred in the last transmit/receive.
Table 2. Command register: read/write (use command 20h/60h)
Bit0 : OBF enable
1 means controller will generate high (interrupt) on P24 when output buffer
has been written.
Bit1 : mouse OBF enable 1 means controller will generate high (interrupt) on P25 when mouse data
comes in output buffer.
Bit2 : system flag
Connect to the status register Bit2.
Bit3 : inhibit override
Write a '1' to this Bit will disable the keyboard inhibit function.
Bit4 : prohibit enabling of Write a '1' to this Bit will disable keyboard interface
keyboard interface
Bit5 : IBM PC keyboard On AT mode, 0 means that the controller will do a IBM keyboard like
type protocol/disable
checking on receiving. On PS2 mode, a '1' disable the mouse interface
mouse interface
Bit6 : PC compatible mode Default is 1, means the scan code translation is on.
Bit7 : reserved.
Table 3. Command List: (with A0 = 1, CS# = 0, RD# = 1, WR# = 0)
20h : read command byte After command execution, OBF = 1 means data is ready on the output
register.
buffer.
60h : write command byte Next byte write to Data port will be written to command byte register.
register.
9xh : write low nibble to
(Port13-Port10).
A1h : controller's version After command execution, OBF = 1 means data is ready on the output
number.
buffer.
A4h : check password
Always return 'F1' on output buffer.
command
A7h : disable mouse
After the command execution, Command byte register bit5 = 1 and P23 = 1
interface
on PS2 mode. No effect on AT mode.
A8h : enable mouse
After the command execution, Command byte register bit5 = 0 and P23 = 0
interface
on PS2 mode. No effect on AT mode.
A9h : mouse interface test. Return 00h if the interface is O.K..
AAh : controller's self test Return 55h if the controller is O.K..
ABh : keyboard interface Return 00h if the interface is O.K..
test.
ADh : disable keyboard
interface.
AEh : enable keyboard
interface.
AFh : return version
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