Operation in the Modbus RTU Network - Master Mode
The CFW500 allows operation as a master for the Modbus RTU network. For this operation, it is necessary to observe the following points:
| • | Only interface RS485 allows operation as a network master. |
| • | It is necessary to program, in product configurations, the operation mode as "Master", besides the communication rate, parity, and stop bits, which must be the same for the whole equipment in the network. |
| • | The Modbus RTU network master does not have an address, so the address configured in the CFW500 is not used. |
| • | Sending and receiving telegrams via RS485 interface using the Modbus RTU is programmed by using blocks in Ladder programming language. It is necessary to know the available blocks and the Ladder programming software in order to be able to program the network master. |
| • | The following functions are available for the sending of requisitions by the Modbus master: |
| o | Function 02: Read Discrete Inputs |
| o | Function 03: Read Holding Registers |
| o | Function 04: Read Input Registers |
| o | Function 05: Write Single Coil |
| o | Function 06: Write Single Register |
| o | Function 15: Write Multiple Coils |
| o | Function 16: Write Multiple Registers |
Blocks to program the master
In order to control and monitor the Modbus RTU communication using the CFW500, the following blocks were developed, and they must be used when programming in Ladder.
