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XW-111™ Wi-Fi Digital Sensor Users Manual
5.4 Read Holding Registers – Modbus Function Code 03 (0x03)
The Read Holding Registers function is used for the voltage status.
Request
32-bit sensor values are read from 16-bit register pairs. Consequently, senors addresses and registers
must be even numbers.
Vin Start Addresses
Start Address: 0x0010 (Vin)
Input Quantity: 0x0002
Response
32-bit floating-point values are returned, either as little-endian or big-endian numbers, depending on the
configuration in the WiFi Networks tab.
With little-endian ordering, a voltage reading (0x0010) would return 0x00004040. The least significant
word would be 0000 hex and the most significant word would be 4040. This hexadecimal value converts
to a voltage reading of 3.0 Volts.
If a voltage reading is not available, a value of 0xFFFFFFFF (NaN) is returned.
Errors
Sensor Read Error Function Code (1 byte): 0x83
Exception Codes (1 byte):
Xytronix Research & Design, Inc.
0x01 – Function not supported.
0x02 – Incorrect combination of start address and input quantity
Modbus/TCP
Page 37
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