Commodore 128 System Manual page 382

11. User Port—Various interface devices can be attached
here.
C-6
User I/O
Pin
Type
1
GND
2 +5V
3 RESET
4
CNT1
5 SP1
6 CNT2
7
SP2
8
PC2
9 SER. ATN IN
10 9 VAC
11
9 VAC
12 GND
Pin Type
A
GND
B FLAG2
C
PB0
D PB1
E
PB2
F PB3
H PB4
J
PB5
K
PB6
L PB7
M
PA2
N
GND
1
2 3 4 5
A B C O E F H J
Pin
1
2
3
4
5
6
7
8
9
Note
MAX. 100 mA
MAX. 100 mA
MAX. 100 mA
Note
6 7 8 9 10 11 12
K L M N
Signal
Ground
Ground
Red
Green
Blue
Intensity
Monochrome
Horizontal Sync
Vertical Sync