Specifications

An EXCEPTION error will be generated if the node cannot

fulfil the task set by the Master or the Slave receives invalid

data in its data slot.

Exception code table

Code Name

01 Illegal Function

02 Illegal Data Address

03 Illegal Data Value

4.3.8 Modbus Codes Reference

Function 4 (04 hex) - read input registers. (3X)

These registers contain the measured and calculated values

of the instrument. Register addresses in the instrument

start at 0 but in keeping with Modicon Modbus codes, are

designated addresses starting at 30001.

Packet from master format :

[Node Addr][04][reg start addr(2 bytes)][No. of reg (2

bytes)] [CRC(2 bytes)]

Response from slave format:

[Node Addr][04](Byte count][Data (byte count

bytes)][CRC(2 bytes)]

The following table lists the parameters with the Modbus

equivalent address and its address within the M550. Any

data requested that isn't applicable to the conditions

column will return the value -ve infinity (FFFFFFFFh)

3X Registers

The registers are listed with their Modbus addresses.

The data held at these addresses are Read-Only.

3X registers are read using function 04h.

M550MAN.PM5 01/08/101, 12:4836