# C64 User Port

(at the computer)

24 PIN MALE EDGE (DZM 12 DREH) at the computer.

Pin | Name | Description
--- | --- | ---
1 | GND | Ground
2 | +5V | +5 VDC (100 mA max)
3 | /RESET | Reset, will force a Cold Start. Also a reset output for devices.
4 | CNT1 | Counter 1, from CIA #1
5 | SP1 | Serial Port 1, from CIA #1
6 | CNT2 | Counter 2, from CIA #2
7 | SP2 | Serial Port 2, from CIA #2
8 | /PC2 | Handshaking line, from CIA #2
9 | ATN | Serial Attention In
10 | +9V AC | +9 VAC (+ phase) (100 mA max)
11 | +9V AC | +9 VAC (- phase) (100 mA max)
12 | GND | Ground
A | GND | Ground
B | /FLAG2 | Flag 2
C | PB0 | Data 0
D | PB1 | Data 1
E | PB2 | Data 2
F | PB3 | Data 3
H | PB4 | Data 4
J | PB5 | Data 5
K | PB6 | Data 6
L | PB7 | Data 7
M | PA2 | PA2
N | GND | Ground

Contributor: Joakim Ögren, Nikolas Engström, Arwin Vosselman, Jestin Nesselroad

Source:
Commodore 64 Programmer's Reference Guide

Copyright © The Hardware Book Team 1996-2001.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2001-06-07