# +4 User Port

Availble on Commodore +4 computer.

(At the Computer)

UNKNOWN CONNECTOR at the Computer.

Pin | Name | Description
--- | --- | ---
1 | GND | Ground
2 | +5V | +5 VDC
3 | /BRESET | ?
4 | P2/CSE | Data 2/Cassette Sense
5 | P3 | Data 3
6 | P4 | Data 4
7 | P5 | Data 5
8 | RxC | Receive Clock
9 | ATN | Attention?
10 | +9V | +9 VAC
11 | +9V | +9 VAC
12 | GND | Ground
A | GND | Ground
B | P0 | Data 0
C | RxD | Receive Data
D | RTS | Request to Send
E | DTR | Data Terminal Ready
F | P7 | Data 7
G | DCD | Data Carrier Detect
H | P6 | Data 6
I | CTS | Clear to Send
J | DSR | Data Set Ready
K | TxD | Transmit Data
L | GND | Ground