Siemens SICAM AK Manual page 78

Redundancy via SCA-RS
A/P-control: only for application-related voting
The state (active or passive) of an entire AU (global redundancy switchover) or the state of a
single BSE or PRE (line-by-line redundancy switchover) is controlled with the help of this
message.
With application-related voting the voter (e.g. control center) generates the required state itself
(e.g. by means of comparing parameterized error messages). The required state of the
system elements is communicated by means of a user data message from the central module.
The message can be parameterized in the OPM (SICAM 1703 + Ax 1703 system functions)
under Redundancy control message with the attributes Control_unction_(RED) (A/P control),
Failure_behavior_(RED), BSE_(RED) and PRE_(RED).
For line-by-line switchover a selective system element (BSE, SSE) is valid as destination
routing.
For global redundancy switchover there is only one A/P control message, which is valid for the
entire automation unit, therefore BSE and SSE are irrelevant.
A set binary information switches the selected system element to active.
If these binary information messages are received with NT-Bit set, either the state is retained
or the system components concerned are switched to passive (can be parameterized in the
failure behavior).
For protocol elements which, based on the parameter setting, belong to a functional
redundancy or a Multimaster, only the A/P control message to the less significant protocol
element is required. However this switches over all associated protocol elements.
User priority: for AU redundancy with SCA-RS
User priority messages in the single point information format are routed to the central
redundancy processing.
The message can be parameterized in the OPM (SICAM 1703 + Ax 1703 system functions)
under Redundancy control message with the attributes Control_function_(RED) (User priority),
Failure_behavior_(RED), BSE_(RED), PRE_(RED) and Priority_RED.
Valid as destination routing for line-by-line switchover
•
one selective system element (BSE, SSE) or
•
all system elements (specific identifier in BSE).
For global redundancy switchover there are only one time priorities, which are valid for the
entire automation unit, therefore BSE and SSE are irrelevant.
For the CPU redundancy the parameterized priorities are valid for the parameterized C-CPU
(BSE) and its protocol elements.
A set binary information increments the counter of the parameterized priorities.
If these binary information messages are received with NT-Bit set, either the state is retained
(counter remains unchanged) or any binary information items previously set are deleted
(counter is decremented, if binary information was set) (can be parameterized in the failure
behavior).
Apart from this user priorities can still be set directly from CAEx plus. For line-by-line
switchover these are valid for the basic system element concerned, for global switchover for
the entire automation unit and for CPU redundancy for the basic system element concerned
and its protocol elements.
In the case of line-by-line or global switchover the integrated totals are sent as system
message to the SCA-RS every 100ms over the system I/O bus. The SCA-RS compares the
priorities of the two automation units, generates the redundancy state and communicates this
to the automation units.
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Unrestricted SICAM RTUs, SICAM AK Redundancy
Edition 10.2016, DC2-026-2.07