RKC INSTRUMENT COM-ML, Инструкция по эксплуатации

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APPENDIX. HOST COMMUNICATION PROTOCOL
IMR02E20-E1
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A.3.2 Function code

Function code contents
Function code
(Hexadecimal)
Function Contents
03H Read holding registers Measured value, control output value, current
transformer input value, Event status, etc.
06H Preset single register Set value, PID constants, event set value, etc.
08H Diagnostics (loopback test) Loopback test
10H Preset multiple registers Set value, PID constants, event set value, etc.

Message length of each function (Unit: byte)
Function code
(Hexadecimal)
Function
Query message Response message
Min Max Min Max
03H Read holding registers 8 8 7 255
06H Preset single register 8 8 8 8
08H Diagnostics (loopback test) 8 8 8 8
10H Preset multiple registers 11 255 8 8
A.3.3 Communication mode
Signal transmission between the master and slaves is conducted in Remote Terminal Unit (RTU)
mode.
Items Contents
Data bit length 8-bit (Binary)
Start mark of message Unused
End mark of message Unused
Message length Refer to A.3.2 Function code
Data time interval Less than 24 bits’ time *
Error check CRC-16 (Cyclic Redundancy Check)
* When sending a command message from the master, set intervals of data configuring one message to time
shorter than the 24 bits’ time. If time intervals become time longer than the 24 bits’ time the relevant slave
assumes that message sending from the master is terminated to deform the message format. As a result, the
slave does not make a response.