Sensor Electronics SEC 3000, Instruction And Operation Manual

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SEC 3120 16-bit Modbus Manual Page 32 Of 46 Sensor Electronics Corporation
For Version 1.2 and above December 2012 P/N 1580282, Rev. 1, 20121228
Here is an example of a request to read Modbus holding registers 42104–42106
from slave device 17, sensor 1 (region 1 = 21xx):
Response
The register data in the response message are packed as two bytes per register,
with the binary contents right justified within each byte. For each register, the first byte
contains the high order bits, and the second byte contains the low order bits.
Here is an example of a response to the query:
The contents of register 42104 are shown as the two byte values of 01 2A hex or
298 decimal. The contents of registers 42105 and 42106 are 01 8F and 03 21 hex, or 399
and 801 decimal, respectively.
Read Holding Register Response
Field Name Example (Hex)
Slave Address
11
Function Code 03
Byte Count 06
Data High Byte (Register 42104) 01
Data Low Byte (Register 42104) 2A
Data High Byte (Register 42105) 01
Data Low Byte (Register 42105) 8F
Data High Byte (Register 42106) 03
Data High Byte (Register 42106) 21
CRC Low Byte 04
CRC High Byte 5D
Read Holding Register Query
Field Name Example (Hex)
Slave Address
11
Function Code 03
Starting Address High 08
Starting Address Low 37
Num Points High 00
Num Points Low 03
CRC Low Byte B4
CRC High Byte F5