# SCSI Internal (Single-ended)

SCSI=Small Computer System Interface.
Based on an original design by Shugart Associates. SCSI was ratified in 1986.

(at the controller & harddisk)
(at the cable.)

50 PIN IDC MALE at the controller & harddisk.
50 PIN IDC FEMALE at the cable.

Pin | Name | Dir | Description
--- | --- | --- | ---
2 | DB0 |  | Data Bus 0
4 | DB1 |  | Data Bus 1
6 | DB2 |  | Data Bus 2
8 | DB3 |  | Data Bus 3
10 | DB4 |  | Data Bus 4
12 | DB5 |  | Data Bus 5
14 | DB6 |  | Data Bus 6
16 | DB7 |  | Data Bus 7
18 | PARITY |  | Data Parity (odd Parity)
20 | GND |  | Ground
22 | GND |  | Ground
24 | GND |  | Ground
26 | TMPWR |  | Termination Power
28 | GND |  | Ground
30 | GND |  | Ground
32 | /ATN |  | Attention
34 | GND |  | Ground
36 | /BSY |  | Busy
38 | /ACK |  | Acknowledge
40 | /RST |  | Reset
42 | /MSG |  | Message
44 | /SEL |  | Select
46 | /C/D |  | Control/Data
48 | /REQ |  | Request
50 | /I/O |  | Input/Output

All odd-numbered pins, except pin 25, are connected to ground. Pin 25 is left open.