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6. Modbus RTU Protocol
The RMV-514 supports the Modbus RTU protocol. The communication Baud Rates range from
2400bps to 115200 bps. The number of data bits is fixed to 8, the parity and stop bits are fixed as no
parity and 1 stop bit.
The Modbus function codes supported in the RMV-514 are 1,2,4,5 and 15. The Modbus address
distribution is as the following table, its Net ID is 1.
6.1 Commands and Description
(1)
Read Digital Output(DO) status (Function code:1)
Request
00
Net ID
1 Byte
01
Function code
1 Byte
02 ~ 03
Starting address
2 Byte
04 ~ 05
DO count
2 Byte
Response
00
Net ID
1 Byte
01
Function code
1 Byte
02
Byte count of response (B=( DO count+7)/8)
1 Byte
03 ~ (B+2)
Bit value
3-(B+2) Byte
(2)
Read Digital Input status (Function code:2)
Request
00
Net ID
1 Byte
01
Function code
1 Byte
02 ~ 03
Starting address
2 Byte
04 ~ 05
DO count
2 Byte
Response
00
Net ID
1 Byte
01
Function code
1 Byte
02
Byte count of response (B=( DO count+7)/8)
1 Byte
03 ~ (B+2)
Bit value
3-(B+2) Byte
(3)
Read Analog Input value (Function code:4)
Request
00
Net ID
1 Byte
01
Function code
1 Byte
02 ~ 03
Starting address
2 Byte
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