Limits for Data Transfer
If the amount of data to be transmitted is greater than the capacity of a
F_SENDDP/F_RCVDP block pair, you can use additional F_SENDDP/ F_RCVDP
block pairs. These require further communication connections. Remember the
maximum limit of 244 bytes of input and 244 bytes of output data for transfer
between an I-slave and a DP master.
The following table shows you how many output and input data are required for
safety-related communication connections:
Required Input and Output Data
Between I-Slave 1 and
DP Master
Between I-Slave 2 and
DP Master
Safety-related
Communication
Communication
Connection
Output Data Input Data Output Data Input Data
Send: I-slave 1 to DP
master
12 bytes 6 bytes - - Master to I-slave
Receive: I-slave 1
from DP master
6 bytes 12 bytes - -
Send: I-slave 1 to I-
slave 2
12 bytes - 6 bytes - I-slave to I-slave
Receive: I-slave 1
from I-slave 2
6 bytes - 12 bytes -
Within the maximum limit of 244 bytes of input and 244 bytes of output data for
transfer between an I-slave and a DP master, remember any master to slave
connections (MS) or direct data exchange connections (DX), on which you
exchange data within your standard user program.
You can check whether you are within the maximum limit of 244 bytes of input and
244 bytes of output data for all the configured safety-related and standard
communication connections in the "Configuration" tab in the object properties of the
I-slave. Include all rows with MODE "MS" in the "Configuration" tab. The rows with
MODE "DX" are not included.
User Acknowledgment
To implement a user acknowledgment in the safety program of the F-CPU of an
intelligent DP slave, refer to the description in Section 1.2.5.
Product Information for the S7 Distributed Safety, Configuring and Programming Manual
38 A5E00169432-02
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