Siemens SIMATIC S7 Manual page 33

General
Information
Range of Values
MODBUS / TCP communication via the integrated PN interface of the CPU
2XV9450-1MB02; Manual edition 2.1
The parameters of the FB MODBUSPN can be divided into two groups:
•
Initialization parameters
•
Runtime parameters
Initialization parameters are evaluated only during the call of OB100 and
are adopted into the instance DB. They are marked with "yes" in the column
"INIT" in the table displayed above.
A modification of the initialization parameters during run mode has no impact.
After a modification of these parameters (e.g. during the test phase), the
instance DB must be initialized again via a STOP
PLC.
Runtime parameters can by modified during the cyclical operation. In the
mode S7 is server, it is not advisable to modify the input parameters while a
request is active. Wait with the next request and the change of the
parameters until the previous request ends with DONE_NDR or ERROR.
In the operation mode S7 is server, the output parameters may only be
evaluated when DONE_NDR is TRUE.
The output parameters are displayed dynamically, i.e. they are only
available for one PLC cycle. They have to be copied to an additional memory
area if you need to process them or to display the values in a VAT (STEP7
variable table).
For the range of values of the different parameters, PLC-specific restrictions
must be taken into consideration.
Function Block MODBUSPN
RUN transition of the
6-7