Functional characteristics
3.3 Characteristics of S7 communication
CM 1542-5
14
Manual, 11/2014, C79000-G8976-C290-02
Diagnostics requests
As a DP master (class 1), the CM 1542-5 supports diagnostics requests of a DP master
(class 2).
DP startup behavior
Note
Increasing the default value for startup parameters - configuration of the CPU
In some situations, it is necessary to increase the default value for the startup parameter
"Parameter assignment time for the distributed I/O" in the configuration of the CPU:
•
When there is a large number of modules (DP slaves) configured that can be assigned
parameters.
•
When a high value is configured for the constant bus cycle time in the network properties
of the PROFIBUS DP line.
3.3
Characteristics of S7 communication
General characteristic data
The following information is important when operating S7 connections:
Table 3- 2
General characteristics of S7 connections
Characteristic
Explanation / values
Number of S7 connections via
PROFIBUS
Operable in total: Max. 48
Configurable: Max. 40
The value depends on the S71500 CPU being used.
Note
PG or HMI functions or data record routing
If PG or HMI functions or data record routing are used, a suitable number of S7 connections
must be reserved during configuration!
Help provided by STEP 7
The number of connections on PROFIBUS shown in the table above can vary due to other
influencing factors. The STEP 7 configuration tool displays warnings and help messages as
soon as limit values are exceeded.
