Siemens SICAM AK Manual page 79

Switch-over disabled: cannot be used for application-related voting
With CPU redundancy and global switchover with SCA-RS it is possible to prevent the
switchover through modified priorities. That is necessary, if e.g. an application is not running
synchronously. The block can be set by means of user data messages or directly in the
function diagrams in CAEx plus, whereby these act OR-linked.
The message can be parameterized in the OPM (SICAM 1703 + Ax 1703 system functions)
under Redundancy control message with the attributes Control_function_(RED) (switchover
disabled) and Failure_behavior_(RED).
For the global switchover the BSE and SSE are irrelevant, as the function is valid for the entire
automation unit.
For CPU redundancy this function can be activated for each CPU pair (parameterize one of
the two C-CPU numbers).
A set binary information blocks the switchover.
If these binary information messages are received with NT-Bit set, either the state is retained
of the block is lifted (can be parameterized in the failure behavior).
With CPU redundancy the blocks set in CAEx plus act OR-linked for the respective CPU pair,
i.e. if one of the C-CPUs has the block set, both C-CPUs are not switched over.
For the global switchover with SCA-RS the block states of all C-CPUs are OR-linked.
The block is indicated in the diagnostic with an error of the diagnostic class Warning.
A/P-control with failed SCA-RS: for AU redundancy with SCA-RS
When using the SCA-RS, this is to be used in a redundant configuration, since when a failure
of the central module is detected, all affected system elements are switched to passive.
If the communication between SCA-RS and M-CPU has failed, then the M-CPU switches all
passive. The SCA-RS switches all active on the functioning connection. With a detected
failure the M-CPU sets all priorities and sends these to the SCA-RS. With that, even if only the
receive line to the M-CPU has failed, the SCA-RS can perform a switchover to the other
automation unit.
If the SCA-RS itself fails, the redundant SCA-RS takes over the function. This state can be
diagnosed in both automation units.
Both automation units are only switched to passive with a failure of both SCA-RS or both
communication lines (double error). Then it is only possible to switch one of the automation
units completely active with specific user data messages in the single point information format.
The message can be parameterized in the OPM (SICAM 1703 + Ax 1703 system functions)
under Redundancy control message with the attributes Control_function_(RED) (A/P-control
with failed SCA-RS) and Failure_behavior_(RED).
The message is valid for the entire automation unit.
A set binary information switches the entire automation unit to active.
If these binary information messages are received with NT-Bit set, either the state is retained
or the automation unit is switched to passive (can be parameterized in the failure behavior).
Listening mode-control
With this message the entire AU is set to this mode. Listening mode means, that the state
passive is always transferred to the interfaces, regardless of which state the A/P-control
message assigns. This is used so that all interfaces do not switch their transmit lines to active
and only listen to the data. Within the AU however the data are still distributed or filtered
based on the active/passive state.
The listening mode is controlled by means of a user data message in the single point
information format.
SICAM RTUs, SICAM AK Redundancy
DC2-026-2.07, Edition 10.2016
Unrestricted
Redundancy via SCA-RS
79