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active operator unit then it takes on the active status itself, otherwise it transitions to passive
status immediately after booting.
1.4.2.10
Disable switchover between TCU via PLC
Overview
The TCU switchover disable offers the option of dynamically disabling switchover from one
TCU to the next when the system is running via the PLC. For the duration of the disable, a
user authorization request to change user authorizations between TCUs will be ignored by the
system and rejected.
The rejected user authorization request causes a message to be output in the dialog line of
the HMI, in the form of a feedback message for the requester. The message disappears after
five seconds.
HMI ↔ PLC data interface
The "switchover disable" function is always active and does not have to be switched on
explicitly. The function is controlled by a data bit in the PLC. The HMI transfers the active OP
to the PLC, thus forming the basis of the control function in the PLC.
The control bits and control information for this function are stored in the m:n data interface of
the PLC. In terms of m:n, this function can be operated separately for the currently overridden
HMIs in both m:n online interfaces (DB19.DBW120 ff for HMI1 and DB19.DBW130 ff for HMI2).
If a system is not running an m:n, only the first m:n online interface is used for this function.
Switchover disable is controlled by a TCU_SHIFT_LOCK bit, managed by the user, on each
HMI in the PLC. The bit address for the first HMI is DB19.DBB126.6 and DB19.DBB136.6 for
the second HMI.
The PLC m:n online interface is expanded so that byte DB19.DBB118 is still added to the first
interface and byte DB19.DBB119 to the second. These bytes acquire the index of the active
TCU (of the active OP) for the appropriate HMI. The byte is called TCU_INDEX. The
appropriate HMI uses the TCU index configured for the active TCU to describe the TCU_INDEX
byte.
The TCU_SHIFT_LOCK bit is monitored by the appropriate HMI. A value = 1 triggers the
switchover disable; switchover is enabled if the value returns to 0. The TCU_SHIFT_LOCK bit
can be set, for example, to the PLC by the user pressing a key or it can be managed by the
PLC user program according to its own logic. The TCU_SHIFT_LOCK bit is managed in the
PLC exclusively by the user; the HMI only accesses this bit in read-only mode.
The HMI assigns the configured index of the TCU or PCU whose OP currently possesses user
authorization in the shadow grouping. If no OP is active, a value of 0 is entered in TCU_INDEX.
If no TCU index is configured for the active TCU (active OP), the value 255 = undefined is
presented as the TCU index. This means that the values 0 and 255 may not be configured as
the TCU index.
Operator panel front: OP 010
Manual, 07/2018, A5E36371538B
General information and networking
1.4 Networking
73
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