Siemens SINUMERIK 840D sl Function Manual page 128

B3: Several operator panels connected to several NCUs, distributed systems - only 840D sl
2.2 Several operator panel fronts and NCUs with control unit management option
Processing operating authorization for servers
Three server-related program branches for handling HMI requests are implemented in the
control unit switchover program:
1. Request for relinquishing operating focus
2. Request for setting operating focus
3. Relinquish operating focus
Each branch checks/processes the first and second HMI interfaces.
The requests are positively acknowledged if no switchover disabling commands are active.
The "Relinquish operating focus" includes deactivation of the relevant machine control panel.
See also diagrams in Section "Examples/Graphic representation of function sequences".
Wait times for acknowledgement signals
To render the program independent of timers, two wait times based on repeated reading of
the system time are implemented via SFC64 in the control unit switchover program. The wait
times for acknowledgement signals can be changed if necessary by means of:
FB101/DB101 variables:
waiting_period_1: Wait for activation/Online HMI
waiting_period_2: Wait for deactivation/offline HMI
Wait for HMI sign of life:
Values can be assigned to the FB101 variables in the range:
0-32 (seconds). These values are entered in ms.
Program integration
If the control unit switchover program on the PLC is to be called as a function in a higher-
level PLC program, then it must be ensured that FB101, FB102 and FC103 and associated
instance data blocks DB101, DB102 have not already been used elsewhere.
Initialization
When the NCU is restarted, all signals relating to control unit switchover on the PLC
interface in DB19 are set to zero.
Note
Before an NCU is initialized, it must be ensured that it is not currently linked online to any
PCU/HT6.
It may be necessary to perform an HMI restart.
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Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Extended Functions