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10 MODBUS RTU, ASCII, TCP
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2. Read commands structure
The master communication device can send commands to the module to read its status and setup or the
measured values, status and setup relevant to the combined counter. More registers can be read, at the same
time, sending a single command, only if the registers are consecutive (see chapter 5).
According to the used MODBUS protocol mode, the read command is structured as follows.
2.1 MODBUS ASCII/RTU
Values contained both in Query or Response messages are in hex format.
Query example in case of MODBUS RTU: 01030002000265CB
Example Byte Description No. of bytes
01 - Slave address 1
03 - Function code 1
00 High
Starting register 2
02 Low
00 High
No. of words to be read 2
02 Low
65 High
Error check (CRC) 2
CB Low
Response example in case of MODBUS RTU: 01030400035571F547
Example Byte Description No. of bytes
01 - Slave address 1
03 - Function code 1
04 - Byte count 1
00 High
Requested data 4
03 Low
55 High
71 Low
F5 High
Error check (CRC) 2
47 Low