Siemens SINUMERIK 840D sl Function Manual page 127

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.
Resetting of interface by PLC
The interface signals relating to control unit switchover can be reset selectively as follows
(without RESET on the NCU):
FB101/DB101 variables:
Initialization
TRUE: Single reset of signals in DB19. After signal reset, the Initialization parameter is
automatically reset to FALSE.
Sign-of-life monitoring
Once a PCU/HT6 is connected online, it sends a sign of life in DB10 DBB108. If a PCU/HT6
in online mode does not send a sign of life signal for longer than the time set in
waiting_period_2, then the PLC program generates the message: "Sign-of-life monitoring
error". This message is not canceled until one of the PCUs/HT6s is switched from offline to
online mode again.
Extended Functions
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Several Operator Panels on Several NCUs, Distributed Systems (B3)
Several operator panel fronts and NCUs with control unit management option
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