Northern Telecom BCS35 Replacement Manual page 139

Figure 13–2xxx
Disk controller (A21A1 and B21A1) circuit pack (680–9143) options
J10
Disk controller circuit pack
Located directly on top of the 72–Mbyte and 140–Mbyte disk drives, this
circuit pack provides data management and data control for Winchester–type
disk drives. The disk controller circuit pack uses as its host interface the
industry standard 8–bit, parallel, bidirectional SCSI bus.
See Table 13–2 for the option settings on this circuit pack. Figure 13–2
shows option locations and circuit pack layout.
W0
W1
W1
J1
SECTOR SIZE
NOT USED
W3, W8
Disk Crossover and Controller circuit packs 123
W0
RAM
1
2
3
4
5
SEQUENCER
6
7
ENC/DEC/VCO
{
W4
W5, W6, W7
DPP Card Replacement Guide BCS35 and up
RAM
BUFFER
Z8 MICROPROCESSOR
EPROM
OPTIONAL
RAM