Verification By The Fb Modbuspn - Siemens SIMATIC S7 Manual

7.2

Verification by the FB MODBUSPN

During Start-up
Cyclical Operation
S7 is Client
MODBUS / TCP communication via the integrated PN interface of the CPU
2XV9450-1MB02; Manual edition 2.1
•
Unambiguousness of the id parameter in the connection parameters
of DB MODBUS_PARAM
•
Parameter group data_type_x, db_x, start_x, end_x. (x = 1 to 8)
1. With data_type_x = 0 the Modbus area is disabled and not
further verified. At least the first area (_1) has to be
parameterized.
2. Validity check of data_type
3. db_x <> 0
4. Test end_x >= start_x
5. Modbus addresses for the same data type defined in two
db_x lead to an error message (address overlap).
Errors during start-up provoke the ERROR bit to remain set. In the cyclical
operation no requests are executed. A correction of the parameterization and
a STOP RUN transition of the PLC are necessary.
Verification when the FB is called:
•
Valid registration key
•
DB MODBUS_PARAM is available with the necessary length
•
Range of values monitoring time RECV_TIME and CONN_TIME
•
Range of values START_ADRESS
•
Range of values LENGTH
•
When executing a request, there also is a check whether the data
block specified by the register or bit address is available and has the
necessary length. The DB number must not be 0 and/or identical to
the number of MODBUS_PARAM or the instance DB.
•
Receipt of the response telegram within the monitoring time
The monitoring time can also elapse if less data than specified in the
MODBUS telegram header is received. Subsequent errors with loss
of telegrams can occur.
Diagnosis
7-3