45
01
Illegal function
The function code is not supported by Meter
02
Illegal Data Address
Attempt to access an invalid address or an
attempt to read or write part of a floating point value
03
Illegal DataValue
Attempt to set a floating point variable to an invalid value
Exception Cases :
An exception code will be generated when Meter receives ModBus query with valid parity
& error check but which contains some other error ( e.g. Attempt to set floating point variable to an invalid value)
The response generated will be “Function code” ORed with HEX (80H ). The exception codes are listed below
Two consecutive 16 bit registers represent one parameter. Refer
TABLE 1
for the addresses of 3X registers
(Parameters measured by the instruments). Each parameter is held in the 3X registers. Modbus Code 04 is used
to access all parameters.
Example :
To read parameter ,
Volts 3 : Start address = 04 (Hex) Number of registers = 02
3.1 Accessing 3 X register for reading measured values:
Note : Number of registers = Number of parameters x 2
Each Query for reading the data must be restricted to 20 parameters or less. Exceeding the 20 parameter limit
will cause a ModBus exception code to be returned.
Query :
Device
Address
Function
Code
Start Address
High
Start Address
Low
Number of
Registers Hi
Number of
Registers Lo
CRC
Low
CRC
High
01 (Hex) 04 (Hex) 00 (Hex)
04(Hex)
00 (Hex)
02(Hex)
30 (Hex) 0A (Hex)
Start Address High : Most significant 8 bits of starting address of the parameter requested.
Start Address low : Least significant 8 bits of starting address of the parameter requested.
Number of register Hi : Most significant 8 bits of Number of registers requested.
Number of register Lo : Least significant 8 bits of Number of registers requested.
(Note : Two consecutive 16 bit register represent one parameter.
)
Response: Volt3 (219.25V)
Device
Address
Function
Code
Byte
Count
Data Register1
High Byte
CRC
High
01 (Hex) 04 (Hex) 04 (Hex) 43 (Hex)
5B (Hex)
41 (Hex)
21 (Hex)
6F (Hex)
Data Register1
Low Byte
Data Register2
High Byte
Data Register2
Low Byte
9B (Hex)
CRC
Low
Byte Count : Total number of data bytes received.
EN