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EtherCAT to Modbus RTU Gateway
Data Field
Data is transmitted in 8-, 16- and 32-bit format. The data for 16-bit registers is transmitted in
high-byte first format. For example: 0x0A0B ==> 0x0A, 0x0B. The data for 32-bit registers is
transmitted as two 16-bit registers, and is low-word first. For example: 0x0A0B0C0D ==> 0x0C, 0x0D,
0x0A, 0x0B.
The data field of messages sent between a master and a slave contains additional information about
the action to be taken by the master or any information requested by the slave. If the master does
not require this information, the data field can be empty.
Reference (Address)
0xxxx
1xxxx
3xxxx
4xxxx
NOTE
For details regarding address mapping (Reference Number) depends on your Modbus RTU slave device.
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Read/Write Discrete Outputs or Coils.
A 0x reference address is used to output device data to a digital output channel.
Read Discrete Inputs.
The ON/OFF status of a 1x reference address is controlled by the corresponding
digital input channel.
Read Input Registers.
A 3x reference register contains a 16-bit number received from an external source,
e.g. an analog signal.
Read/Write Output or Holding Registers.
A 4x register is used to store 16bits of numerical data (binary or decimal), or to
send the data from the CPU to an output channel.
Description
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