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SCSI Crossover circuit pack
– turbo only
General Description
The SCSI Crossover (Xovr) circuit packs are located at positions A15 and
B15 on the inner portion of the hinged card panel at the rear of the A and B
chassis. They are connected between both SCSI Interface circuit packs in
the DPP (A side and B side) and both SCSI Disk Drive assemblies (Disk 1,
disk A at A21; Disk 2, disk B at B21).
The system interface ports of the SCSI Xovr circuit packs (40–pin
connectors Jl & J2) consist of 8 data lines with parity and 12 control lines.
One port is provided for each of the two SCSI Interface cards. The SCSI
port provides the system interface to the SCSI disk drives.
Power from both A and B chassis is provided at this connector in a diode
OR'ed arrangement for redundancy purposes.
The SCSI XOVR circuit packs provide the following functions:
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See Table 14–1 for the jumper setting on this circuit pack. Figure 14–1
shows the circuit pack layout.
Replacing the SCSI circuit pack
To replace the SCSI circuit pack, use the following procedure.
Interface between DPP system backplane (SCSI Interface circuit pack)
and SCSI Disk Drives.
Support for crossover and disk selections for the SCSI Interface circuit
pack.
Support for disconnect/reconnect feature.
Full hardware implementation; no software required.
Two 40–Pin access ports; one for each SCSI Interface circuit pack.
50–pin access port for the disk drive.
4–pin power connector identical to current crossover card.
Either disk drive tristatable off the SCSI bus in case of a fault.
DPP Card Replacement Guide BCS35 and up
131
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