Chipkin™
VeederRoot® Gateway User Manual
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Page 35 of 67
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Interp
reting Modbus Data
Modbus does not have a mechanism for reporting the validity of data. If the gateway loses its
connection to the Veeder-Root device (or a data point cannot be read), it will disregard previous data
as unreliable.
Unreliable data will be tagged with the value 65535 (
‐
1, configurable) in the registers.
Some values have been encoded as IEEE754 format floating point numbers. These values use 2x16-bit
registers and are clearly identified in the Modbus map. Since Modbus does not support floating point
numbers, all values are served as whole numbers.
Modbus Functions Supported (RTU and TCP)
This device supports the following functions:
•
01 (0x01) Read Coils
•
02 (0x02) Read Discrete Inputs
•
03 (0x03) Read Holding Registers
•
04 (0x04) Read Input Registers
Most masters should be configured to use function 3, read holding registers.
Modbus Register Map
The sections contain an example of the Modbus Register Map for this gateway.
Important Note: As mentioned above, this map is based on sample data using a default
configuration. The Modbus Map is generated during the configuration process, so it will
change and will be different than what is described here. You can view the current Modbus
Map by reviewing the Reports page. Follow the instructions found in
VeederRoot
Modbus
# of
Registers
Units
Tank01_tank_product_code
40001
1 no_units
Tank01_tank_tank_status
40002
1 no_units
Tank01_tank_volume
40003
1 us_gallons
Tank01_tank_tc_volume
40004
1 us_gallons
Tank01_tank_ullage
40005
1 us_gallons
Tank01_tank_height
40006
1 inches
Tank01_tank_water
40007
1 inches
Tank01_tank_temperature
40008
1 degrees_Fahrenheit