The following is a list of the default SCSI ID numbers for the Audio
SCSI bus:
ID - 7 (fixed) DARWIN
ID - 6Unassigned
ID - 5Unassigned
ID - 4Jaz Drive (if installed)
ID - 3Unassigned
ID - 2Unassigned
ID - 1Unassigned
ID - 0Internal DARWIN HD (model 4001 only)
Types of SCSI Cables
There are two basic types of SCSI cables in use: DB25 and 50-pin
Centronics. The two types of cable can be identified by their con-
nectors, which are quite different. When buying SCSI extension
cables, it is important to choose ones with the right type of connec-
tors, since the two types will not interconnect without a special
adapter. DB25 connectors are the type commonly found on the back
of personal computers. The SCSI connectors on the DARWIN SCSI
ports are the 50-pin Centronics type. Use only high quality
shielded cables that have all the pins connected. Many cables
only have some of the pins wired.
Terminating SCSI Cables
The total length of the SCSI chain should not exceed 15 feet. A
general rule for SCSI cables is: The Shorter the Better!
Terminating resistors (or terminators) are special resistor packs that
are installed on the first and last device in the SCSI chain. Termi-
nators are used to reduce line echoes or standing waves on the SCSI
bus. An analogy in an audio system would be impedance matching.
Terminators can either be hidden inside a SCSI device or they can
take the form of termination blocks which can simply be plugged
into the SCSI port.
IMPORTANT: DARWIN model 4001, which contains an internal
hard disk, is supplied with an external termination block which
should be attached to the rear panel Audio SCSI Port if no exter-
nal SCSI devices are connected. If you have one or more external
SCSI devices connected to a model 4001, the supplied terminator
block should be connected to the last SCSI device in the chain.
Terminators apply power to an array of resistors to ensure a full 5
volt swing between high and low levels on the SCSI line. The host
system is required to provide Termination Power. Termination power
has its own wire in the SCSI cable and supplies power to the termi-
nation block. On external hard disk drives, SCSI terminator power is
almost always turned Off and the drives are left un-terminated.
DARWIN is shipped with termination power On and internal termi-
nation resistors On. This assumes that the DARWIN will be placed at
one end of the SCSI chain. DARWIN has an automatic system
which ONLY supplies terminator power when it is NOT being
96DARWIN Operation Manual |
ACEC
