Interface for the Modbus RTU
MIQ/2-MOD
22
ba75973e01
07/2012
INT8
All other data are transmitted in the INT8 format. This data consists of
one byte.
The data for the measured value status of the main and secondary
measured values are encoded jointly into a single byte. Bits 7-4 encode
the status of the main measured value, bits 3-0 encode the status of the
secondary measured value.
3.6
Modbus query
With each query of sensor data via the Modbus protocol, a block of con
-
secutive registers is read (up to all of the 32 registers).
For a query of sensor data, determine the first register and the number
of registers to be read (1 ... 32).
Determining the first
register to be read
The first register to be read depends on the sensor number (Sxx) [1 to
4] and the number of the sensor register (R) [1 ... 8]:
(Sxx - 1)] * 8 + R.
Example: Determine the first register with data for the sensor S02:
[(2 - 1) * 8] + 1 = 9
Determining the number
of registers to be read
The maximum number of registers to be read is 32.
Example: Read all data of X sensors
Example of a
Modbus query
and Modbus response
Query of all sensor information of the sensor S02:
Bit representation
Information
High byte
Low byte
MSB
LSB
Number of sensors (X) Number of registers
1
8
2
16
3
24
4
32