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OPTION
SELECTION
Master/Slave CSU
Option
Universal System Shelf (models USS-1D, USS-1-DC/R, and USS-1-
DC/NR)
Up to 16 DataComm 551s or a combination of DataComm 551s and other
plug-ins (including PMC-100 Performance Monitor Cards, DataComm
552 DSUs, and DataComm 596 Modems) can be installed in a rack-
mountable Universal System Shelf. For each group of four DataComm
551s, one CSU-551 Backplane (P/N 048B015-001) must be installed, occupy-
ing four slots (one quadrant) in the shelf.
All rack-mountable housings fit into 19- and 23-inch wide equipment
racks.
Instructions specific to installing the DataComm 551 in the above hous-
ings follow. Refer to the appropriate Instruction Manual for general in-
stallation instructions.
The field-selectable options adapt the DataComm 551 to a variety of con-
figurations, as well as enable or disable certain features and tests. These
options are selected by the positioning of switches and jumper straps on
the pc card. Some of these options may also be selected via the Supervisory
terminal, and stored in non-volatile memory, overriding the switch set-
tings (refer to Supervisory Terminal Operating Procedures in Section 3).
Before selecting any options, consult Tables 2-1 and 2-2 to determine
which options should be selected for your application.
Do not enable Auto Framing for both CSUs on a link.
After determining which options should be selected, see Figure 2-3 (which
describes the method of implementing each option) and Figure 2-1 (which
illustrates the location of each switch and jumper, and its default setting).
Also refer to Section 3, which describes configuring the DataComm 551
via the Supervisory terminal.
The master/slave CSU option provides control over using the Supervisory
terminal to configure the CSU. A master CSU allows configuration via
the Supervisory terminal, while a slave CSU prevents it (changes can be
made only via option switches). Any number of CSUs in the network can
be masters or slaves. There are two means of communication between the
Supervisory terminal and a CSU's Supervisory terminal interface (port):
• In-band communication — the primary means of communicating with
the CSU, utilizing PMC-100s and a dedicated multiplexer channel (i.e.,
a permanent virtual circuit, or PVC). In-band communication is in-
tended for monitoring the CSU's performance reports and performing
other non-disruptive diagnostics and maintenance functions. A typical
in-band communication path is illustrated in Figure 2-4.
NOTE
INSTALLATION
2-5
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