1747-6.22, Backup Scanner User Manual

4-52 Operating Your SLC 500 Backup System
Publication 1747-6.22
The 1747-BSN automatically exchanges system status information
when communicating with another 1747-BSN through the High-
Speed Serial Link (HSSL). Both modules are continuously
communicating with each other, even when both processors are not in
Run mode. This is achieved by sending and receiving the system
status words. This information can be read from either module at any
time and provides for both SLC 5/0x (primary and secondary) the
“other side status”. HSSL is also used to transfer user data table data,
up to 2K total per BSN module.
RS-232/485 Communication Channel
The RS-232/485 channel is a dumb communication channel which is
used to switch the connection to one operator interface or other DF1
device (through RS-232/485). The communication channel relays are
closed when the module is primary; otherwise the relays are open as
shown in the figure below.
Primary Secondary
SLC 5/04 1747-BSN
RIO/DH+ Communication Channel
1747-BSN SLC 5/04
To Operator Interface
The RIO/DH+ communication channel has a relay that is closed when
the 1747-BSN module is in the primary mode; otherwise the relay is
open. The communication channel supports the following
configurations (The illustration on the next page shows the channel
block diagram):
1. RIO: Supports the 57.6, 115.2 and 230.4 KBaud configurations.
When the module is in primary mode, it emulates all the
1747-SN Series B functionality. When the module is in
secondary mode, the channel receives the input data from the
primary 1747-BSN module and sends it to the SLC 5/0x,
emulating the 1747-SN Series B backplane communication. As a
result, the secondary SLC 5/0x “thinks” that it is really
connected to the remote racks;