ADAC Ultra2 S466 Hardware Guide
80
Topic Information
SCSI Bus
Requirements
The ANSI specification dictates the following:
The maximum signal path length between terminators is 3
meters when using up to 4 maximum capacitance (25 pF)
devices and 1.5 meters when using more than 4 devices.
SCSI devices should be uniformly spaced between
terminators, with the end devices located as close as
possible to the terminators.
The characteristic impedance of the cable should be 90 +/-
6 ohms for the /REQ and /ACK signals and 90 +/- 10 ohms
for all other signals.
The stub length(the distance from the controller’s external
connector to the mainline SCSI bus) shall not exceed.1m
(approximately 4 inches).
The spacing of devices on the mainline SCSI bus should be
at least three times the stub length.
All signal lines shall be terminated once at both ends of the
bus powered by the TERMPWR line.