Disk Crossover And Controller Circuit Packs; General Description; Replacing Disk Controller Circuit Pack - Northern Telecom BCS35 Replacement Manual

Disk Crossover and Controller
circuit packs

General description

These circuit packs provide the data and control paths between the Disk
Interface circuit pack in the card rack and the disk drives: 72 – 380 Mbyte
w/o 56K or compression polling. For 380 Mbyte, 760 Mbyte, or 1.7 Gbyte
disk drives w/56Kpolling or compression polling, see Section 14: SCSI
Crossover pack.
The Disk Crossover (Xovr) circuit pack is on the inside of the hinged panel,
A15 and B15, at the rear of each DPP chassis. This pack provides a
crossover data path between the processors and the disk. The program in the
active processing unit controls this pack which simultaneously routes data
from the active Disk Interface circuit pack to both disk drives.
For 380– and 760–Mbyte disk drives, the Disk Controller circuit pack is
inside the disk drive. For the 72– and 140–Mbyte drives, the Disk
Controller circuit pack is on the top of the disk assembly. This circuit pack
is in the data path between the Disk Xovr circuit pack and the disk drive.
The Disk Controller circuit pack is a smart circuit assembly, containing a
processor, RAM, EPROM, and additional control circuitry. Control signals
(status commands, write signals, and read signals) are passed through this
pack, which initiates the appropriate operation in the disk drive.
See Table 13–1 for the jumper option setting on the Disk II Crossover circuit
pack. Figure 13–1 shows the jumper location and circuit pack layout. The
Disk Controller options are described in Table 13–2.

Replacing Disk Controller circuit pack

Use the following procedure when replacing the Disk Crossover circuit
pack.
DPP Card Replacement Guide BCS35 and up
115