(A) Input Port Definition (AT Mode)
BIT
FUNCTION
0
Undefined
1
Undefined
2
Undefined
3
Undefined
4
RAM on System Board
0: Disable second 256 KB of system board RAM
1: Enable second 256 KB of system board RAM
5
Manufacturing Jumper Installed
0: Manufacturing jumper
1: Jumper not installed
6
Display Type Switch
0: Primary display attached to color/graphics
1: Primary display attached to monochrome
7
Keyboard Inhibit Switch
0: Keyboard inhibited
1: Keyboard not inhibited
(B) Output Port Definition (AT Mode)
BIT
0
System Reset
1
Gate A20
2
Undefined
3
Undefined
4
Output Buffer Full
5
Input Buffer Empty
6
Keyboard Clock (Output)
7
Keyboard Data (Output)
FUNCTION
(C) Test-input Port Definition (AT Mode)
BIT
0
Keyboard Clock (Input)
1
Keyboard Data (Input)
FUNCTION
9