XLINK 500/100 Operations & Maintenance Manual page # 173
Modbus Reg Type
Modbus Reg Type needs to correspond to the type of register that contains the desired sensor
data. Options include Coil, Discrete, Holding, and Input. Please check the sensor’s
documentation for details on registers.
Coil and Discrete register types imply that the station will collect one byte from the sensor and
consider the least significant bit of the byte.
Modbus Reg Number
Modbus Reg Number tells the station
which of the sensor’s registers to access. These values are
unique to the sensor that is connected. Most sensors provide multiple registers which may be
read.
Modbus Value
Modbus Value tells the station how much data to collect and how to interpret it.
Short means collect data from one register and interpret them as a 16 bit signed integer.
Ushort implies a 16-bit unsigned integer.
Int and Uint indicate 32 bit signed and unsigned values respectively; the station will
read 2 registers for them.
Float is a IEEE 32 bit floating point value.
Double is a IEEE 64 bit floating point value.
Discrete means that the sensor returns one byte and that the result is based on the least
significant bit of the byte.
Modbus MSW
For certain Modbus Value (Int, Uint, Float, Double), Modbus MSW determines which register is
used to contain the most significant word (MSW) of the tag's value. When set to "Low Reg", the
lower register of the register pair is used to contain the MSW.
Modbus Timeout
Modbus Timeout is the amount of time in seconds that the station will wait for a reply from the
sensor.
Modbus Retries
Modbus Retries indicates how many times the station will retry to issue the command to a
sensor in case of failures. Please note that some sensors require at least one retry to work at all.
For those sensors, the initial command only wakes the sensor up after which the sensor replies
to the retry.
18.4.
Modbus Slave Function Codes
The following table identifies the functions that are supported. Each diagnostic counter is
cleared when the device is powered up or reset.
Code
Hex
Subcode
Hex
Read Holding Registers
0x03
Read Input Register
0x04
Write Single Register
0x06
Diagnostic
0x08
Return Query Data
0x00
Diagnostic
0x08
Clear Counters
0x0A