Siemens SINUMERIK 840D sl Function Manual page 210

Several Operator Panels on Several NCUs, Distributed Systems (B3)
Examples
We must differentiate between two cases here:
1. MMC_1 can change to passive operating mode:
2. MMC_1 cannot change to the passive operating mode (processes which do not permit a
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MMC_1 changes from active to passive operating mode and acknowledges the
changeover with
MMC1_ACTIVE_CHANGED = FALSE.
If an MCP is assigned to the MMC and activated, it is now deactivated by the PLC.
The PLC gives permission for a changeover to the active operating mode with
MMC2_ACTIVE_PERM = TRUE.
MMC_2 changes state and acknowledges with MMC2_ACTIVE_CHANGED = TRUE. If
an MCP is assigned to MMC_2, it is now activated by the PLC.
changover are running on MMC_1):
MMC_1 sets MMC1_CHANGE_DENIED = TRUE, the change of state cannot be
completed.
The PLC acknowledges with MMC1_CHANGE_DENIED = FALSE and gives permission
to MMC_1 to remain in active mode with MMC1_ACTIVE_PERM = TRUE. By sending
MMC2_CHANGE_DENIED = TRUE, it notifies MMC_2 that MMC_1 cannot switch over to
passive mode.
MMC_2 then acknowledges with MMC2_CHANGE_DENIED = FALSE and remains in
passive operating mode.
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Extended Functions