Communications Capabilities
S5-115F Manual
Processing Send and Receive mailboxes
The Send and Receive mailboxes can only be processed with SINEC L1 synchronization.
Synchronization is performed:
•
Automatically by the operating system
•
By calling FB 254 with the "SINEC L1 processing" parameter in the user program.
Synchronization of SINEC L1 processing takes place automatically every 30 to 40 ms in the
operating system. We therefore recommend that you also carry out synchronization every 30 to
40 ms in the user program by calling FB 254 with the "SINEC L1 processing" parameter.
To maintain data consistency, you should always process the Receive and Send mailbox in a
continuous program sequence. Processing must be completed before the next SINEC L1
synchronization takes place.
To ensure that the program sequence is not interrupted, you should inhibit interrupt processing
(IA statement).
Example:
There are six possible data paths for interslave communications when using three slaves. Only the
following four data paths should be implemented, however:
Partner
Slave 1
Slave 2
Slave 3
Data paths
Slave 1 provides slaves 2 and 3 with information via central control. In addition, data is exchanged
between slaves 2 and 3 in both directions. These four data paths correspond to the following
mailboxes:
Slave 1 :
Send mailbox for data
to Slave 2
Send mailbox for data
to Slave 3
No Receive mailbox
Slave 2 :
Send mailbox for data
to Slave 3
Receive mailbox for data
from Slave 1
Receive mailbox for data
from Slave 3
Slave 3 :
Send mailbox for data
to Slave 2
Receive mailbox for data
from Slave 1
Receive mailbox for data
from Slave 2
For the user program in Slave 2 in the example this means:
Slave 2 writes data for slave 3 to receive into the Receive mailbox of slave 3. Note here that writing
is completed before the user calls the next FB 254 SYNC. If the SINEC L1 data path is free and if
FB 254 ”SYNC processing” has been possible in the receiving slave 3, the contents of the mailbox
are transferred by calling FB 254 SYNC and arrive in the Receive mailbox of slave 3.
The Send mailbox in slave 2 can be processed with the next FB 254 ”SYNC processing”, but this is
not mandatory.
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EWA 4NEB 811 6148-02
