7705 SAR Interfaces
172
Interface Configuration Guide
3HE 11011 AAAC TQZZA Edition: 01
3.6 Surveillance, Control, and Data Acquisition
(SCADA) Support
SCADA systems are used in many strategic industry networks, such as utility and
transportation, to monitor and maintain the networks from remote monitoring
locations. SCADA systems use a master/slave architecture with a single master that
supports multiple slave remote terminal units (RTUs).
Nokia addresses the needs of SCADA customers with the Integrated Services card.
The Integrated Services card is a resource card that is capable of supporting
software applications that specifically meet the requirements of TDM-based SCADA
systems. The card is supported on the 7705 SAR-8 and the 7705 SAR-18.
The Integrated Services card supports the following SCADA applications:
• multidrop data bridge (MDDB)
• pulse code modulation (PCM) multidrop bridge
• voice conference bridge (VCB)
Only one application can be active on the card at a time.
The MDDB and PCM multidrop bridge applications feature similar architecture and
functionality, with the main exception being that the MDDB application uses a serial
RS-232 or X.21 interface, while the PCM multidrop bridge application uses an E&M
analog interface. The VCB application builds on the PCM architecture, using A-Law
or Mu-Law encoding and an E&M analog interface.
3.6.1 Multidrop Data Bridge
The MDDB application provides a centralized digital bridging functionality that allows
a SCADA bridge to be configured between a master and remote slaves. The bridge
allows a single data message stream to be broadcast from a master to multiple
slaves and allows a single slave to communicate back to the master.
In a SCADA network, the 7705 SAR provides the communications infrastructure to
connect the central masters to multiple RTUs at remote locations, where the masters
and RTUs communicate over serial RS-232 or X.21 links (synchronous or
asynchronous). The 7705 SAR-8 or 7705 SAR-18 located at the master site contains
the Integrated Services card, which provides the MDDB bridge functionality and acts
as the MDDB master. Remote 7705 SAR nodes connected to RTUs are referred to
as MDDB slaves.
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