Characteristics Of S7 Communication - Siemens CM 1542-1 Operating Instructions Manual

Note
Connection resources of the CPU
Depending on the CPU type, different numbers of connection resources are available. The
number of connection resources is the decisive factor for the number of configurable
connections. This means that the values that can actually be achieved may be lower than
specified in this section describing the CM.
You will find detailed information on the topic of connection resources in the function manual
/4/ (Page 50).
Restrictions for UDP
● Restrictions UDP broadcast / multicast
To avoid overloading the CP due to high broadcast / multicast frame traffic, the receipt of
UDP broadcast / multicast on the CP is limited
● UDP frame buffering
Length of the frame buffer: At least 7360 bytes
Following a buffer overflow, newly arriving frames that are not fetched by the user
program are discarded.
1.3.4

Characteristics of S7 communication

S7 communication provides data transfer via the ISO-on-TCP protocol.
Characteristic
Total number of freely usable S7 connections on
Industrial Ethernet
LAN interface - data field length generated by CM
per protocol data unit (PDU = protocol data unit)
Note
Maximum values for an S7-1500 station
Depending on the CPU you are using, there are limit values for the S7-1500 station. Note the
information in the relevant documentation.
CM 1542-1
Operating Instructions, 07/2019, C79000-G8976-C355-04
Properties and functions
1.3 Configuration limits and performance data
Explanation / values
Max. 64
for sending: 480 bytes / PDU
•
for receiving: 480 bytes / PDU
•
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