Siemens SIMATIC S7 Configuration And Programming Manual page 38

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:
Safety-related Communication
Communication Connection
Master to I-slave Send: I-slave 1 to DP
master
Receive: I-slave 1
from DP master
I-slave to I-slave Send: I-slave 1 to I-
slave 2
Receive: I-slave 1
from I-slave 2
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.
38
Required Input and Output Data
Between I-Slave 1 and
DP Master
Output Data
12 bytes
6 bytes
12 bytes
6 bytes
Product Information for the S7 Distributed Safety, Configuring and Programming Manual
Between I-Slave 2 and
DP Master
Input Data Output Data
6 bytes -
12 bytes -
- 6 bytes
- 12 bytes
Input Data
-
-
-
-
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