SCSI Physical Characteristics
Chapter 5
Technical Reference Manual
Page 51
CFP2107E (WIDE, 80-pin Single Connector Attachment [SCA])
External Terminator Power
The interface connector carries both power and ground so a separate TERMPWR
interface line is not provided.
Internal Termination
This version of the drive has no on-board termination so the drive must be
externally terminated. Alternative 2 active termination is recommended.
Alternative 1 passive termination is not suitable for this application.
Cable Requirements
This version of the drive is designed to facilitate interfacing directly to a mating
connector which is on a passive back plane or directly into a motherboard.
The design of the SCSI bus interconnect system should meet the following
guidelines, particularly with FAST SCSI-2 systems:
•
Do not route the data signals next to any high frequency or large current
switching signals. Unreliable drive operation can result from improper
signal routing.
•
Signal line stubs should not exceed 0.1 meter (4 inches).
•
There should be 0.3 meters (12 inches) of transmission line between drives.
•
The total length of any signal line should not exceed 6 meters (20 feet) and
may have to be reduced if excessive impedance discontinuities exist on the
bus.
•
Maintain a minimum of 0.050 inches (1.27mm) gap between adjacent
signal.runs to control crosstalk between signal lines.
•
Signals routed over a ground plane or between ground planes have different
characteristic impedance. Signals with critical timing like REQ, ACK and
Data should be routed similarly.
The signal length between devices should either be spaced shorter than the stub
length, which treats a group of devices as a lumped element, or far enough apart
that a transmission line exists (0.3 meters or 12 inches). These signal length
considerations should include the length of signal traces and connectors on the
printed circuit board. The diagram below shows how it is possible to
interconnect six 1-inch height drives over a relatively short length of
interconnect.
3" [0.08m]
maximum
12" [0.3m] minimum
