Keeping the World Flowing
17
4.4 Redundant Systems – RedCom Redundancy
The RedCom Dual Channel Profibus DP Option Card version
has two redundant communications channels. Like the Simple
card, the RedCom card supports two types of redundant
operation and the details are as described in Profibus
Guideline 2.212 ‘Specification Slave redundancy’. The two
modes are:
•
SR – System Redundancy
(One common slave address)
•
FR – Flying Redundancy
(Two slave addresses offset by 64)
The Rotork Profibus DP RedCom Dual Channel
Option Card obeys the Profibus REDCOM
Specification for Redundant Communications.
This includes 3 bytes of Extended Diagnostics for
RedState. Not all PLC systems can accept these
diagnostic messages.
As with the Simple Redundant card, there are two basic
considerations when looking at redundant systems;
protection against the failure of the connecting cable and
protection against failure of the device. Most systems
consider cable protection to be the most important and this
is termed ‘SR’ or System Redundancy. The alternative setup,
using only a single cable, but with two Profibus connections
is termed ‘FR’ or Flying Redundancy. With FR systems there
are two Profibus interfaces on the slave, but only one slave,
so protection against failure of the Profibus interface is
included. SR and FR are described in more detail in the
previous section.
Control System Master
Probus Probus
Redundant Slave
Interface Card
Actuator
Primary Slave Backup Slave
Red Extensions Red Extensions
Fig. 10: Profibus DP RedCom Dual Redundant Option
Block Diagram
The Profibus DP RedCom Dual Channel card includes:
•
Two Profibus Connections, Channel 1 and Channel 2
•
RedCom link between the two connections
•
Redundancy extensions to the V1 protocol
•
No loss of data during switching
•
Selectable FR/SR mode
•
Status reported in Extended Diagnostics data
Single and Dual Data Highway Configurations
A4 US
US
A4
US
A4
A4 US
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