SMAR MB-700, User Manual

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MB-700 – User’s Manual
7.2
MB-700 Module Redundancy
Terminology
Role: User configuration which defines the module as Main or Backup.
State
: Module state which depends on the conditions that both are, and also the Role configuration.
The possible states are Active and Standby.
Active:
State which indicates basically if the module is executing the function blocks, which will be
responsible for the Scan of the net and data update.
Standby:
State which the MB-700 monitors the manner and the performance of the other block, for
an eventual necessity to be as Active. It keeps constantly updated with regard to processed data for
Active, through the redundant communication channel.
Main:
It is an user configuration which defines which module must be preferentially Active. Thus, if
both MB-700s are in good conditions to execute the function blocks (including the Modbus
communication), the configured module as Main will be the Active module.
Backup:
It is a user configuration which defines which module must pass the control to the other
when they are in the same operation conditions. And will must assume as Active when occurs a
failure in the other MB-700 module.
Hot Standby:
Redundancy schematic where it has an active element and other constantly alert
monitoring the active condition, maintaining constantly updated to assume the control from the last
condition.
Local:
It is the MB-700 module with which it is communicating and supervising. Remember that the
MB-700 Standby module can be supervisioned, that is, the MB-700 standby block parameters which
are copies of the MB-700 Active block parameters, can be monitored.
Remote:
Almost all MB-700 Active data base is transferred to the MB-700Standby, but some
information does not fit in this case, for example, the redundancy configuration (Role) and the state.
Through the IDShell Transducer Block it is possible to know not only the MB-700 (Role)
configuration and the State, which is being supervising (Local), but also the other MB-700 (Remote),
because this information is exchange between both by the redundancy communication channel.
Communication channel for redundancy:
It is the communication channel between the MB-
700modules in order to synchronize both, that is, the configuration of both is always equal and the
process dynamic variables are constantly transferred.
Switchover:
Control switching from one module to other, that is, a MB-700 which is Standby
becomes to Active.
System Pre-requirements
The requirements listed here apply to both redundancy modes.
The version of firmware for redundant systems has the termination "R". It indicates a firmware
suitable for redundant applications. With the redundant firmware, the module initializes by default in
Hot Standby mode, in a safety state called “Sync_Idle”. The user as will be seen forth can change
the redundancy mode later, if necessary.
The
SYSCON configuration should be created as it is usually done for a non-redundant system (in
case of questions, please refer to Chapter 3 of this manual). The unique difference (now that
redundancy is involved) is that it is necessary to add a transducer function block to the bridge. This
transducer will be used then to initialize the redundancy.
In the
SYSCON configuration, the tag for the transducer block can be any, preferentially a
meaningful tag concerned to the MB-700 tag or to the plant. Be careful to not use tags already in
use in the same plant.