Siemens SIMATIC S7 CP340 Programming Manual page 60

5 MODBUS RTU Protocol communication
5.3.4 Equipment connection
Use standard RS232C cable to connect serial ports of CP441-2 interface1 and
computer. The detailed cable connecting method may be seen in CP441 Manual -
Appendix B: Connecting cables.
5.3.5 Communication test
1. Modbus slave test software is also used. Please refer to the above-stated
operation steps for CP341 test. The slave is set as shown in the Fig. below:
Fig. 108: Setting of Modbus Slave test software
2. Set M8.0 as TRUE in Step7 Variable table to enable receive, and trigger M0.0
in manual way to produce rising edge to enable send. The data communication
results may be shown as in the Fig. below.
Fig. 109: Online monitoring of communication status
CP340/CP341/CP440/CP441 Communication and Programming
Entry-ID: 88867653, V1.0, 02/2014
corresponds
to DB2.DBB1
corresponds to
DB2.DBB0
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