w83c42 Winbond Electronics Corp America, w83c42 Datasheet - Page 9

• Manufacturer Part Number: w83c42
• Description: Keyboard Controller
• Manufacturer: Winbond Electronics Corp America

Status Register, continued
OUTPUT BUFFER
The output buffer is an 8-bit read-only register at I/O address hex 60. The keyboard controller uses
the output buffer to send the scan code received from the keyboard and data bytes required by
command to the system. The output buffer should be read only when the output buffer full bit in the
register is 1.
INPUT BUFFER
The input buffer is an 8-bit write-only register at I/O address hex 60 or 64. Writing to address hex 60
sets a flag that indicates a data write; writing to address hex 64 sets a flag that indicates a command
write. Data written to I/O address hex 60 are sent to the keyboard (unless the keyboard controller is
expecting a data byte) following the controller's input buffer only if the input buffer full bit in the status
register is set to 0.
I/O PORTS
The keyboard controller has two 8-bit I/O ports and two test inputs. One of the ports is assigned for
input and the other for output. The controller uses the test inputs to read the state of the keyboard's
clock line and data line.
The following figures show bit definitions for the input, output, and test-input ports.
(A) Input Port Definitions
BIT
6
7
BIT
0
1
2
3
4
5
Receive Time Out
Parity Error
BIT DESCRIPTION
Undefined
Undefined
Undefined
Undefined
RAM on System Board
0: Disable 2nd 256 KB of System Board RAM
1: Enable 2nd 256 KB of System Board RAM
Manufacturing Jumper Installed
0: Manufacturing Jumper
1: Jumper Not Installed
0: No Receive Time Out Error
1: Receive Time Out Error
0: Odd Parity (No Error)
1: Even Parity (Error)
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FUNCTION
FUNCTION
Publication Release Date: July 1994
W83C42
Revision A3