Varec 4000 manual Modbus Implementation

Modbus Implementation Tank Gauge Transmitter

Function	Function	Information Type	Modbus Nomenclature
Code
01	Read	Bits	Read output status
02	Read	Bits	Read input status
03	Read	Integer, Code, Status word,	Read output registers
		Floating point
04	Read	Integer, Code, Status word,	Read input registers
		Floating point
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,	Preset multiple registers
		Floating point
65	Read	Floating point	Read floating point registers
66	Write	Floating point	Write floating point registers

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.

Configuration Item	Valid Entries	Modbus	Model 1200
		Configurable	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,	No	Yes
	4800, 9600
Number of Stop Bits	1 or 2	No	Yes
Parity	Odd, Even, None	No	Yes

Table 9-2: Modbus Configuration Information

46 Installation and Operations Manual