IBM 5150 - Page 51

Hex PAO
Port I
1
Number N
2
0060
0061
0062
0063
Note:
P
U
3
T
4
5
6
7
PBO
o 1
U 2
T 3
P 4
U 5
T 6
7
1-+---;
PCO
I 1
N
2
P
3
U
4
T
5
6
7
'--'---'
+ Keyboard Scan Code 0
1
2
3
Or
4
5
6
7
-
+ Timer 2 Gate Speaker
+ Speaker Data
+ (Read Read/Write Memory Size) or (Read Spare Key)
+ Cassette Motor Off
- Enable Read/Write Memory
- Enable I/O Channel Check
- Hold Keyboard Clock Low
- (Enable Keyboard or + (Clear Keyboard and Enable Sense Switches)
I/O Read/Write Memory (SW2-1)]-
I/O Read/Write Memory (Sw2-2)
I/O Read/Write Memory (Sw2-3)
I/O Read/Write Memory (Sw2-4)
+ Cassette Data In
+ Timer Channel 2 Out
+ I/O Channel Check
+ Read/Write Memory Parity Check
Command/Mode Register
Mode Register Value
PA3
PA2
Sw1-4
Sw1-3
1 1
PA5
PA4
Sw1-6
Sw1-5
0
0
0 1
1
0
1 1
PA7
PA6
Sw1-8 Sw1-7
0 0
0 1
1
0
1 1
r--
IPL 5-1/4 Diskette Drive (SW1 -1)
Reserved (SW1-2)
System Board Read/Write * (SW 1 - 3)
Memory Size
System Board Read/Write *(SW1-4)
Memory Size
+ Display Type 1
+ Display Type 2
No.
of 5-1/4 Drives
No.
of 5-1/4 Drives
'--
* *(SW1-5)
* *(SW1-6)
* * *(SW1-7)
* **(SW1-8)
Hex 99
3 2
I/O Read/
Binary
Write
Value
Memory
X
32K
(Sw2-5)
1 0 I
Amount of Memory
Located on System Board
64 to 256K
Display at Power-Up Mode
Reserved
Color 40 X 25 (BW Mode)
Color 80 X 25 (BW Mode)
IBM Monochrome (80 X 25)
Number of 5-1/4" Drives
in
System
1
2
3
4
A plus
(+) indicates a bit value of 1 performs the specified function.
A minus (-) indicates a bit value of 0 performs the specified function.
PA Bit =0 implies switch' 'ON." PA bit =1 implies switch' 'OFF."
8255A I/O Bit Map
1-32 System Board