Varec 4000 User Manual
Page 56

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