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1.3.3
Ultra SCSI
1-4
Connectors J3 and J6 are shielded 68-pin VHDCI right-angle receptacles
that protrude through the back panel bracket. See
location of these connectors.
Differential SCSI active termination is provided on the LSIU40HVD.
Termination is automatically enabled when only one of the connectors J2
and J3 (or J5 and J6) is used, or when an 8-bit device is connected to
the 16-bit J3 or J6 connectors. The LSIU40HVD supplies SCSI bus
TERMPWR (termination power) through a blocking diode and a
self-resetting 1.5 A short circuit protection device. An on-board LED
lights when TERMPWR is off. Separate jumpers for each channel allow
user override of termination.
A 40 MHz oscillator is installed on the LSIU40HVD to provide the clock
frequency to the LSI53C876 chip that is necessary to support Wide Ultra
SCSI transfers of up to 40 Mbytes/s.
The LSIU40HVD has full support for Ultra SCSI as well as supporting
Fast SCSI simultaneously. Ultra SCSI is an extension of the SCSI-3
family of standards that expands the bandwidth of the SCSI bus, allowing
faster synchronous data transfers. Special SCSI cables are specified for
operation with Ultra SCSI devices, and you must consider the total
number of devices and the length of your SCSI bus when setting up your
system. See the section on connecting your SCSI peripherals in
Chapter 2, "Installing the LSIU40HVD,"
of SCSI bus connections.
Using the LSIU40HVD
Figure 2.1
for a more detailed explanation
for the
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