IBM 5150

I/O Address Map
PAO
+KBD SCAN CODE
IPL 51/4 DISKETTE DRIVE
(SW1-1)
I
1
RESERVED
(SW1-2)
N
2
SYS. BD. READ/WRITE MEMORY SIZE
• (SW1-3)
X'OOSO'
P
3
3
SYS. BD. READ/WRITE MEMORY SIZE
• (SW1--4)
U
4
4 OR
+DISPLAY TYPE 1
(SW1-5)
T 5
5
+DISPLAY TYPE 2
(SW1-6)
6
6
NO. OF 5 1/4 0 RVS
(SW1-7)
7
7
NO. OF 51/4 DRVS
(SW1-8)
PBO +TIMER 2 GATE SPEAKER
0 1 +SPEAKER DATA
U 2
+(READ READ/WRITE MEMORY SIZE) OR (READ SPARE KEY)
X'OOSJ'
T 3 +CASSETTE MOTOR OFF
P 4
-ENABLE READ/WRITE MEMORY
U
5
-ENABLE I/O CH CK
T
S
-HOLD KBD CLK LOW
7
-(ENABLE KBD) OR + (CLR KBD & ENABLE SENSE SW'S)
PCO
I/O READiWRITE MEMORY (SW2-n]- ] [ SPARE KEY (SW2-5)
I 1 I/O READiWRITE MEMORY (SW2-2) BINARY OR
N
2
I/O READiWRITE MEMORY (SW2-3) VALUE
X'0062'
P
3
I/O REAOiWRITE MEMORY (SW2-4) X 32KB
U 4 +CASSETTE DATA IN
T
5
+TIMER CHANNEL 2 OUT
6
+1/0 CHANNEL CHECK
7
+READiWRITE MEMORY PCK
X'0063'
CMD/MODE REGISTER
MODE REG VALUE
7 6
4 3
o
1 0 1 1
o 1
X'99'
PA3
PA2
AMOUNT OF MEMORY
SW1-4 SW1-3
LOCATED ON SYS. BD.
o
o 16K BYTES
o
1
32K BYTES
1 o 48K BYTES
1
1 64K BYTES
PA5
PA4
TYPE OF DISPLAY
SW1-S SW1-5
o
o
RESERVEO
o
1
COLOR CARD 40X25 (BW MODE)
o COLOR CARD 80X25 (BW MODE)
1
IBM MONOCHROME DISPLAY (80 X 25)
PA7 PAS
NUMBER OF 5-1/4" DRIVES
SW1-8 SW1-7 IN SYSTEM
o o
1
o
2
3
4
8255A - I/O BIT MAP
NOTE: PA bit=O implies switch "ON".
PA bit=1 implies switch "OFF".
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