w83977eg Winbond Electronics Corp America, w83977eg Datasheet - Page 70

• Manufacturer Part Number: w83977eg
• Description: Winbond Isa I/o W83977ef W83977eg
• Manufacturer: Winbond Electronics Corp America

8. KEYBOARD CONTROLLER
The KBC (8042 with licensed KB BIOS) circuit of W83977EF/EG is designed to provide the functions
needed to interface a CPU with a keyboard and/or a PS/2 mouse, and can be used with IBM
compatible personal computers or PS/2-based systems. The controller receives serial data from the
keyboard or PS/2 mouse, checks the parity of the data, and presents the data to the system as a byte
of data in its output buffer. Then, the controller will assert an interrupt to the system when data are
placed in its output buffer. The keyboard and PS/2 mouse are required to acknowledge all data
transmissions. No transmission should be sent to the keyboard or PS/2 mouse until an acknowledge
is received for the previous data byte.
8.1
The output buffer is an 8-bit read-only register at I/O address 60H (Default, PnP programmable I/O
address LD5-CR60 and LD5-CR61). The keyboard controller uses the output buffer to send the scan
code received from the keyboard and data bytes required by commands to the system. The output
buffer can only be read when the output buffer full bit in the register is "1".
8.2
The input buffer is an 8-bit write-only register at I/O address 60H or 64H (Default, PnP programmable
I/O address LD5-CR60, LD5-CR61, LD5-CR62, and LD5-CR63). Writing to address 60H sets a flag
to indicate a data write; writing to address 64H sets a flag to indicate a command write. Data written to
I/O address 60H is sent to keyboard (unless the keyboard controller is expecting a data byte) through
the controller's input buffer only if the input buffer full bit in the status register is “0”.
Output Buffer
Input Buffer
Multiplex I/O PINS
GP I/O PINS
KINH
Keyboard and Mouse Interface
P17
P12~P16
W83977EF-AW/W83977EG-AW
8042
-68-
P25
P21
T0
P24
P20
P27
P10
P26
P23
T1
P22
P11
MCLK
MDAT
KIRQ
MIRQ
KDAT
KCLK
GATEA20
KBRST
®
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