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Characteristic
Maximum data length for program blocks
LAN interface max. data field length generated
by the CM per protocol data unit (TPDU =
transport protocol data unit)
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 66).
Restrictions for UDP
• Restrictions UDP broadcast / multicast
To avoid overloading the CM due to high broadcast/multicast frame traffic, the receipt of
UDP broadcast/multicast on the CM 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.
SIMATIC CM 1542-1
Operating Instructions, 04/2023, C79000-G8976-C355-05
1.5 Configuration limits and performance data
Explanation / values
Program blocks allow the transfer of user data in the following lengths:
1. ISO-on-TCP, TCP: 1 - 64 kbytes
2. UDP
CM with article number 6GK7542-1AX00-0XE0:
–
1 - 1452 bytes
–
CM with article number 6GK7542-1AX10-0XE0:
1 - 2048 bytes
3. E-mail (job header + user data): 1 - 256 bytes
e-mail attachment: ≤ 64 kbytes
•
For sending
–
ISO-on-TCP, TCP: 1452 bytes / TPDU
•
For receiving
–
ISO-on-TCP: 512 bytes / TPDU
–
TCP: 1452 bytes / TPDU
Properties and functions
17
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