w83977ctf Winbond Electronics Corp America, w83977ctf Datasheet - Page 91

• Manufacturer Part Number: w83977ctf
• Description: Winbond I/o
• Manufacturer: Winbond Electronics Corp America

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.
HKBRST (Hardware Keyboard Reset)
A "1" on this bit selects hardware KB RESET control logic to control KBRESET signal.
A "0" on this bit disables hardware KB RESET control logic function.
When the KBC receives data that follows a "D1" command, the hardware control logic sets or clears
GATE A20 according to the received data bit 1. Similarly, the hardware control logic sets or clears
KBRESET depending on the received data bit 0. When the KBC receives a "FE" command, the
KBRESET is pulse low for 6 S(Min.) with 14 S(Min.) delay.
GATEA20 and KBRESET are controlled by either the software control or the hardware control logic
and they are mutually exclusive. Then, GATEA20 and KBRESET are merged along with Port92
when P92EN bit is set.
6.5.2 Port 92 Control Register (Default Value = 0x24)
SGA20 (Special GATE A20 Control)
A "1" on this bit drives GATE A20 signal to high.
A "0" on this bit drives GATE A20 signal to low.
PLKBRST (Pull-Low KBRESET)
A "1" on this bit causes KBRESET to drive low for 6 S(Min.) with 14 S(Min.) delay. Before issuing
another keyboard reset command, the bit must be cleared.
NAME
NAME
BIT
BIT
= 0 0
= 0 1
= 1 0
= 1 1
KCLKS1
Res. (0)
7
7
KCLKS0 Reserved Reserved Reserved
Res. (0)
KBC clock input is 6 Mhz
KBC clock input is 8 Mhz
KBC clock input is 12 Mhz
KBC clock input is 16 Mhz
6
6
Res. (1)
5
5
-82 -
Res. (0)
4
4
Res. (0)
3
3
Publication Release Date: March 1999
Res. (1)
P92EN
W83977EF/ CTF
2
2
PRELIMINARY
HGA20
SGA20
1
1
Revision A1
PLKBRST
HKBRST
0
0