Commodore 64 / 128 User I/O pinout

#Computer#Buses and Slots

24 pin DZM 12 DREH connector  at the computer

24 pin DZM 12 DREH connector  at the computer

Top side
1GNDGround
2+5VDC(100 mA max)
3/RESETReset, will force a Cold Start. Also a reset output for devices.
4CNT1Serial port counter from CIA #1
5SP1Serial port from CIA #1
6CNT2Serial port counter from CIA #2
7SP2Serial port from CIA #2
8/PC2Handshaking line from CIA #2
9ATNThis pin is connected to the ATN line of the serial bus
10+9VAC(+ phase) Connected directly to the Commodore 64 transformer (100 mA max)
11+9VAC(- phase) Connected directly to the Commodore 64 transformer (100 mA max)
12GNDGround
Bottom side
AGNDGround
B/FLAG2The Commodore 64 gives you complete control over Port B on VIA chip #1. Eight lines for input or output are available, as well as 2 lines for handshaking with an outside device. The I/O lines for Port B are controlled by two locations. One is the port itself, and is located at 56577 ($DD01 hex). Naturally you PEEK it to read an input, or POKE it to set an output. Each of the eight I/O lines can be set up as either an input or an output by setting the data direction register properly. It is located at 56579 ($DD03 hex).
CPB0
DPB1
EPB2
FPB3
HPB4
JPB5
KPB6
LPB7
MPA2
NGNDGround

CDTV Memory Card connector pinout

CommodoreVic 20 Memory Expansion connector pinout