Specifications

Publication 1747-SG001E-EN-E - February 2013
Select Network Communications 63
The 1747-BSN module contains the full complement of RIO scanner features, plus
backup capability for support of redundant processor applications. The backup system
consists of one or more pairs of complementary modules, with one module residing in the
primary system and the other in the backup system. The primary system controls the
operation of remote I/O, while the backup system monitors communications via the
high-speed serial link (HSSL) and is available to take control in the event of a fault in the
primary system.
The 1747-BSN features:
• backup of one Remote I/O or DH+ network per complementary BSN module
pair.
• backup of one RS-232/DH-485 communications per complentary BSN module
pair,
• allowing HMIs on channel 0 to automatically transfer to the primary processor.
• transfer of up to 2 K words of retentive data per BSN.
• repair of primary system fault during secondary backup system operation.
• remote programming capability of secondary processor on DH+ (SLC 5/04
only).
• minimal user program impact.
• backup system diagnostic information.
Remote I/O Adapter Module
The 1747-ASB module provides a communication link between SLC or PLC scanners
and a wide variety of 1746 I/O modules over the Remote I/O link. The module maps the
image of the I/O modules in its remote chassis directly to the SLC or PLC image table.
The 1747-ASB module features:
• support for both discrete and block transfer image mapping.
• efficient image utilization with support for 1/2-slot, 1-slot, and 2-slot addressing.
Direct Communication Module
The 1747-DCM module links the SLC 500 controller to the Allen-Bradley PLC for
distributed processing. The DCM acts as a remote I/O adapter on a remote I/O link.
Information is transferred between a local PLC or SLC scanner and a remote
1747-DCM module during each remote I/O scan. The number of DCMs that a scanner
can supervise depends on the number of chassis the scanner supports and the chassis size
of the DCM. The SLC 500 module controllers support multiple DCMs.
Note: An important distinction between a DCM module and the 1747-ASB module is
that a DCM is placed in the chassis with the processor and it does not scan any I/O in the
chassis as an ASB module does.