Fail-Safe Blocks
Fail-Safe Systems
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8.3 Blocks for F Communication Between CPUs
To ensure additional safety-related data exchange between Safety Programs on
different CPUs, additional fail-safety-related information is also transferred as well
as the actual user data. This information and the associated mechanisms remain
hidden to the user.
The following blocks are available for F communication:
Block Description
F_SENDBO Send F_BOOL data to another CPU
F_RCVBO Receive F_BOOL data from another CPU
F_SENDR Send F_REAL data to another CPU
F_RCVR Receive F_REAL data from another CPU
ID and R_ID Addressing Parameters for F Communication Blocks
• ID is the reference to the local connection description. ID is assigned during
connection configuration (NetPro). The I/O ID must be assigned parameters on
the sending side (F_SENDBO, F_SENDR) and on the receiving side
(F_RCVBO, F_RCVR).
• Via R_ID you can define that a sending and a receiving fail-safe block belong
together: The associated fail-safe blocks receive the same value for R_ID. The
value R_ID is a freely selectable odd number, but it must be unique for a
sending/receiving F block pair.
Note
The value R_ID + 1 is also assigned and must not be used.
TIMEOUT Parameter
All four blocks for F communication have the TIMEOUT parameter for vital-sign
monitoring of the communication between the CPUs. You can find out how to
calculate TIMEOUT in the section entitled "Configuring the Monitoring Times for
F/FH Systems".
Note
Data transfer takes place cyclically. It can only be guaranteed that a signal level to
be transferred will be detected on the sender side and transferred to the recipient if
it is present for at least as long as the configured monitoring time (TIMEOUT).
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