SCSI Q Connector Pin Out

The SCSI-3 Standard defined the Single-Ended 'Q' cable. The main SCSI page; SCSI Bus Description.
The Single-Ended Q-cable is used to provide wide-SCSI. The pinout for the Q cable is listed in the table below.
Information on other SCSI cables or detailed descriptions of the different SCSI standards are provided by links after the pin out table.

SCSI Q Connector PinOut
[Single-Ended Data]
Pin # Pin Function Pin # Pin Function
1 Ground 35 Data bit 28
2 36 Data bit 29
3 37 Data bit 30
4 38 Data bit 31
5 39 Parity bit 3
6 40 Data bit 16
7 41 Data bit 17
8 42 Data bit 18
9 43 Data bit 19
10 44 Data bit 20
11 45 Data bit 21
12 46 Data bit 22
13 47 Data bit 23
14 48 Parity bit 2
15 49 Ground
16 50 Ground
17 Termination Power 51 Termination Power
18 Termination Power 52 Termination Power
19 Reserved 53 Reserved
20 Ground 54 Ground
21 55 Terminated
22 56 Ground
23 57 Terminated
24 58 -ACKQ
25 59 Terminated
26 60 Terminated
27 61 Terminated
28 62 Terminated
29 63 -REQQ
30 64 Terminated
31 65 Data bit 24
32 66 Data bit 25
33 67 Data bit 26
34 68 Data bit 27

Note that each pin has its own ground return pin, which is the best possible design.

The "A" cable is used with SCSI-1, SCSI-2, or SCSI-3 to provide "FAST" SCSI with an 8 bit [Parallel] data bus. Refer here for the main SCSI Bus page.
With SCSI-2 the "A" may be used alone or with the "B" cable to provide "WIDE" SCSI allowing a 16 or 32 bit data bus. The pin-out for the 'A' cable is listed on the SCSI Bus 'A' connector page.

The "B" Single-Ended cable pinout is listed on the SCSI Bus 'B' connector page.
On SCSI-3, the "A" cable may be used for an 8 bit data bus. However the new "P" cable is used to provide a 16 bit data path (wide SCSI). To allow 32 bits of data the "P" cable is combined with another new cable called "Q" (wide SCSI). The "Q" cable pin-out [Single-Ended Data] is listed above, see SCSI Bus 'Q' Differential connector page.
The pin-out for the 'P' cable is listed on the SCSI Bus 'P' connector page.

Back to the main SCSI Interface Bus page
The SCSI [parallel] bus width is either 8 bits or 16 bits [Wide bus]. Also the bus may be either Single ended or Differential; however the two are mutually exclusive SCSI is a chained parallel bus, cables start at the Host and run from device to device in a chain. SCSI may be used for asynchronous and synchronous transfers; Asynchronous transfers using Start and Stop bits and synchronous transfers using system timing (Hand-Shaking). The data bus also carries one parity bit.

There are a number of key words associated with SCSI, including; Parallel SCSI, Direct Attached Storage [DAS], Networked Attached Storage [NAS],
and Storage Area Network [SAN].

This cabling interface will be found on older and out-dated computer gear.
The interface originated on SCSI 3 devices beginning in 1995 and used up until SCSI 4 was released in 2002.

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Modified 3/05/12
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