Product guide

7
ATTO Technology Inc. ExpressPCI UL5D, UL4S, UL4D Host Adapter Installation and Operation Manual
3.1 Cabling and termination
Cables and devices must be chosen to maximize performance and minimize the electrical noise from the
high-speed data transfers available with the SCSI protocol. Cabling and termination methods become
important considerations.
The following table lists the maximum number of
devices you may connect at specific cable
distances using differential and single-ended
SCSI in various SCSI environments.
Exhibit 3-2 The development of SCSI capabilities
Cable types
Use high quality Ultra 320-rated, well-insulated
SCSI cables to ensure error free communications.
The illustration at right depicts several internal
and external cable connectors.
Setting up cables and termination
The ExpressPCI Ultra320SCSI host adapter
supports two types of SCSI signaling: Low
Voltage Differential (LVD) and Single-Ended.
Devices on the same SCSI bus must use the same
signaling, either LVD or Single-Ended.
To set up cabling and termination:
1 Determine whether you are using a single
channel or dual channel host adapter model.
One external connector indicates a single
channel host adapter; two external connectors
indicate a dual channel host adapter.
2 Determine if SCSI devices are going to be
installed internally or externally.
• Total bus cable length varies by host
adapter and type of attached devices.
Refer to Exhibit 3-2 for details on maximum
cable length.
STA terms
Bus speed
MB/sec. max.
Bus width
bits
Max. bus lengths, meters
Max. device
support
Single-ended LVD HVD
SCSI-1
586 - 25 8
Fast SCSI
10 8 3 - 25 8
Fast Wide SCSI
20 16 3 - 25 16
Wide Ultra/WIDE SCSI
40 16 - - 25 16
Wide Ultra/WIDE SCSI
40 16 1.5 - - 8
Wide Ultra/WIDE SCSI
40 16 3 - - 4
Ultra2 SCSI
80 16 - 12 - 16
Ultra160 SCSI
160 16 - 12 - 16
Ultra320SCSI
320 16 - 12 - 16