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Application and functions
1.4 Performance data and behavior in operation
1.4.5
Characteristics of S7 communication
General characteristic data
The following information is important when operating S7 connections:
Characteristic
Number of operable S7 connections
Dependencies and restrictions relating to the number of S7 connections
Depending on the configuration and modes, remember the following:
● The actual possible number of S7 connections that can be operated depends on the type
of CPU being used. Further restrictions result from multiprotocol mode; note the
information in the section Parallel use of communications services (multiprotocol mode)
(Page 18)
● If the CP is configured as a DP slave, the following restrictions apply:
– S7 connections cannot be operated;
– OP multiplex mode is not possible.
Execution times for program blocks for S7 connections
The following table will help you to calculate the CPU cycle times (OB1) for S7 connections.
The table contains the execution time of the program blocks (PUT, GET, USEND, URCV,
BSEND, BRCV) required for DP processing on the S7-300 / C7-300 CPU.
Block type
Data length
CPU 314C-2DP
(6ES7 314-
6CF00-0AB0)
CPU 317-
2PN/DP (6ES7
317-2EJ10-
0AB0)
16
Execution time on the CPU per block call
PUT
GET
<=160 bytes
<5.6 ms
<5.8 ms
<2.1 ms
<2.5 ms
Explanation / values
16 maximum
S7 connections configured at one end / both
ends; including PG and TD/OP connections
USEND
URCV
<6.0 ms
<5.6 ms
<2.0 ms
<2.4 ms
Manual, 07/2017, C79000-G8976-C146-10
BSEND
BRCV
<=16 K bytes
<5.7 ms
<5.8 ms
<2.1 ms
<2.7 ms
CP 342-5 / CP 342-5 FO
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