Xylem H-3553 - Manual (Page 33)

Below are some examples of Modbus commands and their format.
Example #1: Read Holding Register Command:
Format: “aabbccccddddeeee”
Where: aa = 1 byte Modbus address
bb = 1 byte function code
cccc = 2 byte start address
dddd = 2 byte quantity of registers
eeee = 2 byte crc check
Example:
010300010001D5CA
Modbus Operation
31
Table 5-5: Baud Rate Select Register Options
Table 5-6: Parity Select Register Options
Stage Slope Register
The Stage Slope holding register allows the user to enter a user defined stage slope. Writing to this register
is only applicable when the Stage Units Select Register is set to 06, which indicates the user defined mode
for the units. The factory default slope is 2.3067, which is the slope for stage unit’s feet. See Chapter 4 – Stage
Slope for more information. This holding register is a 32-bit holding register. Therefore, the value sent to write
to this register must be in a 32-bit floating point number format.
Stage Register
The Stage holding register holds the current measured stage value. This holding register is a 32-bit holding
register. Stage is the result of the pressure in the line multiplied by the stage slope and added to the stage
offset.
Pressure Register
The Pressure holding register holds the current measured pressure value before the slope and offset is
applied. Therefore, it holds the raw PSI value. This holding register is a 32-bit holding register.
Temperature Register
The Temperature holding register holds the current measured temperature. The temperature reading is the
temperature of the internal pressure sensor and may not accurately reflect air temperature.
Control Battery Register
The Control Battery holding register holds the current measured battery connected to the control circuit
board or sensor interface cable power connections. This holding register is a 32-bit holding register.
Tank Pressure Register
The Tank Pressure holding register holds the current measured tank pressure value. This holding register is a
32-bit holding register.
Compressor Battery Register
The Compressor Battery holding register holds the current measured battery connected to the compressor
power input on the H-3553 box. This holding register is a 32-bit holding register.
Modbus Command Examples