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Modbus Implementation Tank Gauge Transmitter
46 Installation and Operations Manual
Table 9-1: Modbus Functions
Note! Exception: Because the ATT does not distinguish between inputs and outputs, function codes 01 and 02 as they apply
to bits, and function codes 03 and 04 as they apply to numeric values refer to the same data registers. For example,
either function code 03 or function 04 can be used to read the integer form of the true mass variable at data address
0053.
Table 9-2: Modbus Configuration Information
Function
Code
Function Information Type Modbus Nomenclature
01 Read Bits Read output status
02 Read Bits Read input status
03 Read Integer, Code, Status word,
Floating point
Read output registers
04 Read Integer, Code, Status word,
Floating point
Read input registers
05 Write Bits Force single output status
06 Write Integer, Code, Status word Preset single register
08 n/a Repeat of Loopback Message Loopback test
15 Write Bits Force multiple outputs
16 Write Integer, Code, Status word,
Floating point
Preset multiple registers
65 Read Floating point Read floating point registers
66 Write Floating point Write floating point registers
Configuration Item Valid Entries Modbus
Configurable
Model 1200
Configurable
Modbus Address 1 to 254 No Yes
Maximum Integer Size Whole number (0 to 65,534) Yes Yes
Integer Scaling Factors Floating point number Yes Yes
Unit Selection Coding list Yes Yes
Baud Rate 300, 600, 1200, 2400,
4800, 9600
No Yes
Number of Stop Bits 1 or 2 No Yes
Parity Odd, Even, None No Yes