Page 137 - Gas Detection Systems Training Manual
P. 137
Query
The query message specifies the register reference to be preset. Registers are addressed starting at zero: register 1 is addressed as 0.
Here is an example of a request to preset register 42106 to set high alarm set point as 1200 in slave device 17, for sensor 1:
Preset One Sensor High Set Point Holding Register Query
Field Name
Slave Address Function Code Address High Address Low Data High
Data Low
CRC Low Byte CRC High Byte
Example (Hex)
11 06 08 39 44 B0 6B 83
Preset ALL Sensor High Set Point Holding Registers Query
Field Name
Slave Address Function Code Address High Address Low Data High
Data Low
CRC Low Byte CRC High Byte
Example (Hex)
11 06 07 D5 44 B0 A9 62
The normal response is an echo of the query, returned after the register contents have been preset.
Response
Here is an example of a response to the query shown above:
Preset One Sensor High Set Point Holding Register Response
Field Name
Slave Address Function Code Address High Address Low Data High
Data Low
CRC Low Byte CRC High Byte
Example (Hex)
11 06 08 39 44 B0 6B 83
Preset ALL Sensor High Set Point Holding Registers Response
Field Name
Slave Address Function Code Address High Address Low Data High
Data Low
CRC Low Byte CRC High Byte
Example (Hex)
11 06 07 D5 44 B0 A9 62
SEC 3120 16-bit Modbus Manual Page 36 Of 46 Sensor Electronics Corporation For Version 1.2 and above December 2012 P/N 1580282, Rev. 1, 20121228
