W83977ATF Datasheet, PDF (206/207 Pages) Winbond – WINBOND I/O

6.4 Commands, continued
COMMAND
D1h
D2h
D3h
D4h
E0h
FXh
W83977ATF
PRELIMINARY
FUNCTION
Only set/reset GateA20 line based on the system data bit 1
Send data back to the system as if it came from Keyboard
Send data back to the system as if it came from Auxiliary Device
Output next received byte of data from system to Auxiliary Device
Reports the status of the test inputs
Pulse only RC(the reset line) low for 6µS if Command byte is even
6.5 HARDWARE GATEA20/KEYBOARD RESET CONTROL LOGIC
The KBC implements a hardware control logic to speed-up GATEA20 and KBRESET. This control
logic is controlled by LD5-CRF0 as follows:
6.5.1 KB Control Register (Logic Device 5, CR-F0)
BIT
7
6
5
4
3
NAME KCLKS1 KCLKS0 Reserved Reserved Reserved
2
P92EN
1
0
HGA20 HKBRST
KCLKS1, KCLKS0
This 2 bits are for the KBC clock rate selection.
= 0 0 KBC clock input is 6 Mhz
= 0 1 KBC clock input is 8 Mhz
= 1 0 KBC clock input is 12 Mhz
= 1 1 KBC clock input is 16 Mhz
P92EN (Port 92 Enable)
A "1" on this bit enables Port 92 to control GATEA20 and KBRESET.
A "0" on this bit disables Port 92 functions.
HGA20 (Hardware GATE A20)
A "1" on this bit selects hardware GATEA20 control logic to control GATE A20 signal.
A "0" on this bit disables hardware GATEA20 control logic function.
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Publication Release Date:April 1998
Revision 0.52