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Block Diagram
SCSI Interface
3
SCSI Termination
3-6
The MVME2603/2604 VMEmodule supports mass storage
subsystems through the industry-standard SCSI bus. These
subsystems may include hard and floppy disk drives, streaming
tape drives, and other mass storage devices. The SCSI interface is
implemented using the Symbios 53C825A SCSI I/O controller at a
clock speed of 40MHz. The SCSI I/O controller connects directly to
the PCI local bus.
The MVME2603/2604 routes its SCSI lines through the P2
connector to the MVME712M transition module (as illustrated in
Figure
1-22). The SCSI control lines have filter networks to
minimize the effects of VMEbus signal noise at P2.
The SCSI bus is 16 bits wide in systems that support the VME64
extension (i.e., those equipped with 5-row, 160-pin VME backplane
connectors). The SCSI bus is 8 bits wide in VME systems that do not
support the extension. Refer to the MVME712M User's Manual for
the pin assignments of the SCSI connectors used on the transition
module. Refer to the Symbios 53C825A data manual for detailed
programming information.
The individual configuring the system must ensure that the SCSI
bus is properly terminated at both ends.
In MVME712M I/O mode, the MVME2603/2604 base board uses
the sockets provided for SCSI bus terminators on the P2 adapter
board used with the MVME712M. If the SCSI bus ends at the
adapter board, termination resistors must be installed there. +5Vdc
power to the SCSI bus
supplied through a fuse located on the adapter board.
In MVME761 I/O mode, the P2 adapter board used with the
MVME761 has a jumper to enable/disable SCSI bus terminators.
+5Vdc power for SCSI termination is supplied through a
polyswitch located on the adapter board.
signal and termination resistors is
TERMPWR
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