Default id, Terminating the scsi chain – Nikon LS-10 Installation Guide for Macintosh User Manual
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The SCSI Interface
Chapter 3
pencil or pen, since these will discolor the switch and make it hard to differentiate the
ON versus OFF position.
Never
use SCSI ID #7 for a SCSI device, as it is reserved for the Macintosh.
Default ID
DIP Switch Configuration
SCSI ID
DIP#1
DIP #2
DIP #3
0
Off
Off
Off
1
On
Off
Off
2
Off
On
Off
3
On
On
Off
4
Off
Off
On
5
On
Off
On
6
Off
On
On
Table 3.2
Configuration DIP switch values for corresponding SCSI ID number.
SCSI ID #5 indicates factory default setting.
Terminating the SCSI Chain
The
SCSI chain
is the electrical bus connecting two or more SCSI devices. It is
critical that this bus be correctly terminated for the SCSI devices to operate properly.
Termination
is an electronics term that applies to the impedance found at both
ends of the bus. The electrical signals on the SCSI bus are changing rapidly between
their digital ‘on’ and ‘off states. To minimize electrical ‘noise,’ a
terminator 'is
placed on
each end of the SCSI bus. The effects of this termination may be unseen to you, but are
critical nonetheless.
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Incorrect SCSI termination can cause unpredictable errors.
Typically, the Macintosh internal SCSI connector has a hard disk drive connected
to it and is terminated. Quadra models have a special internal SCSI cable which has ter
mination installed at the end of the cable. All internally mounted SCSI devices in
Quadra 9Ü0/950 systems should
nothe.
terminated.
If one other SCSI device shares the SCSI bus, it also must be terminated. If addi
tional SCSI devices sit on the bus in between the two end SCSI devices, these devices
cannot
be terminated.
The SCSI chain will only operate properly if termination is in place
at the beginning and end of the SCSI bus.
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