w83977atf Winbond Electronics Corp America, w83977atf Datasheet - Page 206

• Manufacturer Part Number: w83977atf
• Description: Winbond I/o
• Manufacturer: Winbond Electronics Corp America

6.4 Commands, continued
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)
KCLKS1, KCLKS0
This 2 bits are for the KBC clock rate selection.
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.
NAME
= 0 0
= 0 1
= 1 0
= 1 1
BIT
COMMAND
D1h
D2h
D3h
D4h
FXh
E0h
KBC clock input is 6 Mhz
KBC clock input is 8 Mhz
KBC clock input is 12 Mhz
KBC clock input is 16 Mhz
KCLKS1
7
KCLKS0 Reserved Reserved Reserved
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 6 S if Command byte is even
6
5
- 102 -
4
FUNCTION
3
Publication Release Date:April 1998
P92EN
2
W83977ATF
PRELIMINARY
HGA20
1
Revision 0.52
HKBRST
0