Avago Technologies LSI53C120 - Manual (Page 14)

1-2 Introduction
In both SCSI Bus Extender and Converter modes, cable segments are
electrically isolated from each other. This feature maintains the signal
integrity of each cable segment. For bus isolation applications, the
LSI53C120 is ideally suited for the LSI53C875 Ultra SCSI controller.
The LSI53C120 provides additional control capability through the pin
level electrical isolation mode. This feature permits logical disconnection
of both the A-side bus and the B-side bus without disrupting SCSI
transfers currently in progress. For example, devices on the logically
disconnected B-side can be swapped out while the A-side bus remains
active.
The LSI53C120 is based upon bus expander technology resulting in
some signal filtering and re-timing to maintain signal skew budgets. In
addition, the LSI53C120 has no programmable registers, therefore, it
does not require any software.
Figure 1.1 LSI53C120 SCSI Bus Device
Single-ended Wide Ultra SCSI Bus
(Data and Control)
A-Side B-Side
LSI53C120
SCSI Bus
Expander
40 MHz Oscillator
Control Signals Differential Wide Ultra SCSI Bus
(Data and Control)
or
Single-ended Wide Ultra SCSI Bus
(Data and Control)