Specifications

SCSI-BUS TERMINATION

To provide error-free operation of the SCSI bus system, it is absolutely necessary that the

SCSI bus is electrically terminated in a correct way. You can imagine the SCSI bus being a

single cable which must be actively terminated at each ends of the cable. The individual

SCSI devices are then being connected to the cable directly between these terminated ends,

and the SCSI controller itself also acts as a SCSI device (please also see Figure 7).

In the real-world application this means that the first and the last SCSI device in the SCSI

chain must be actively terminated, and the connection to the controller must be made

somewhere between the first and the last device. There is also one special case, which is the

possible translation from a WIDE SCSI bus (16 bit data) to a Fast SCSI bus (8 bit data). At

this point, all data lines which are only implemented on the WIDE SCSI bus (the upper 8 data

lines) must be terminated actively, while the lower 8 data lines must then be terminated at

the end of the Fast SCSI bus. Therefore it is necessary to use WIDE to Fast SCSI adaptors

with the described integrated termination when Fast SCSI devices shall be connected to the

CYBERSTORM PPC SCSI controller.

The CYBERSTORM PPC SCSI controller doesn't have an own active termination, as there

are too many possible custom configurations. The termination will be done either with SCSI

devices at the end of the chain, or - in case only one SCSI device is connected to the SCSI

bus - with an additional active terminator (see Figure 8).

Figure 8.

A correct connected

Ultra-WIDE-SCSI

harddrive

on the

CYBERSTORM PPC

Ultra-Wide-SCSI

Controller

connector of the Ultra-

WIDE-SCSI Controller

on the CYBERSTORM PPC

activ

terminated

Ultra-Wide-SCSI

harddisk

active

terminator

Older SCSI devices such as hard disks, removable drives, or streamers mostly have passive

terminators installed. These terminators are usually located nearby the SCSI connector of the

device. These passive terminators can not be used on the SCSI bus of the CYBERSTORM

PPC SCSI controller, and must always be removed as the SCSI bus must be actively

terminated. If these passive termination resistors (usually resistor arrays) are not socketed,

which is sometimes the case with devices where the termination resistors are SMD soldered,

they can usually be disabled by a jumper or a switch on the SCSI devices. In any case,

please refer to the

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