The SCSI-3 Standard defined the
Differential 'Q' cable. The Differential Q-cable is used to provide
wide-SCSI.
The pinout for the Q cable is listed in the table below, providing pin functions or signal names.
Information on other SCSI cables or detailed descriptions of the
different SCSI standards are provided by links after the pin out table.
The SCSI Bus page contains the main SCSI description.
Note that the SCSI interface is out-dated, which makes the Q-cable also old technology.
| Pin # | Pin Function | Pin # | Pin Function |
| 1 | Data bit 28 + | 35 | Data bit 28 - |
| 2 | Data bit 29 + | 36 | Data bit 29 - |
| 3 | Data bit 30 + | 37 | Data bit 30 - |
| 4 | Data bit 31 + | 38 | Data bit 31 - |
| 5 | Parity bit 3 + | 39 | Parity bit 3 - |
| 6 | Ground | 40 | Ground |
| 7 | Data bit 16 + | 41 | Data bit 16 - |
| 8 | Data bit 17 + | 42 | Data bit 17 - |
| 9 | Data bit 18 + | 43 | Data bit 18 - |
| 10 | Data bit 19 + | 44 | Data bit 19 - |
| 11 | Data bit 20 + | 45 | Data bit 20 - |
| 12 | Data bit 21 + | 46 | Data bit 21 - |
| 13 | Data bit 22 + | 47 | Data bit 22 - |
| 14 | Data bit 23 + | 48 | Data bit 23 - |
| 15 | Parity bit 2 + | 49 | Parity bit 2 - |
| 16 | Differential sensing | 50 | Ground |
| 17 | Termination Power | 51 | Termination Power |
| 18 | Termination Power | 52 | Termination Power |
| 19 | Reserved | 53 | Reserved |
| 20 | Terminated | 54 | Terminated |
| 21 | Ground | 55 | Ground |
| 22 | Terminated | 56 | Terminated |
| 23 | +ACKQ | 57 | -ACKQ |
| 24 | Terminated | 58 | Terminated |
| 25 | Terminated | 59 | Terminated |
| 26 | Terminated | 60 | Terminated |
| 27 | Terminated | 61 | Terminated |
| 28 | +REQQ | 62 | -REQQ |
| 29 | Terminated | 63 | Terminated |
| 30 | Ground | 64 | Ground |
| 31 | Data bit 24 + | 65 | Data bit 24 - |
| 32 | Data bit 25 + | 66 | Data bit 25 - |
| 33 | Data bit 26 + | 67 | Data bit 26 - |
| 34 | Data bit 27 + | 68 | Data bit 27 - |
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' Single Ended
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.
The term SCSI means Small Computer Systems Interface.
SCSI defines and electrical and physical Interface for a parallel peripheral bus.
SCSI interfaces can be found in peripheral computer hard drive data Buses, Direct Attached Storage [DAS] systems, Networked Attached Storage [NAS] devices and Storage Area Network [SAN] components.
Navigation > Engineering Home > Interface Buses > Cable Buses > SCSI Bus > Differential SCSI 'Q' Cable.
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