Chapter 4
Installing the Drive
Page 28
Filepro CFP2107 Series
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
These guidelines apply to both cabled and backplane implementations.
Guidelines specifically for cabled implementations can be found on page 35.
While it is possible to connect SCA drives using a cable, users should be aware
that the mating connector is designed for 0.025 inch (0.63 mm) pitch 30 AWG
wire. There are four +12 volt and three +5 volt line pairs carrying power to the
drive on the SCA so spin up must be staggered to connect two drives on the same
cable and the cable length kept to a minimum. Otherwise, there should only be
one drive per cable.
Attaching Power to the Drive - CFP2107E
The drive is powered through the SCA connector.
