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.
| 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.
Navigation > Engineering Home > Interface Buses > Cable Buses > SCSI Bus > Single-Ended SCSI 'Q' Cable.
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