3 data field, 4 error check (checksum) field, 5 5-1.2 exception responses – RLE 10K V.2.5.a User Manual

Page 30: Table 4.1, Exception codes

SeaHawk 10K User Guide

800.518.1519

Modbus Communication

4.1.1.3 Data

Field

The length of the data field varies depending on the function. The data fields for the

SeaHawk 10K are 16-bit registers, transmitted high order byte first (big-endian).

4.1.1.4 Error Check (Checksum) Field

The checksum field lets the receiving device determine if the packet has transmission errors.

The SeaHawk 10K RTU mode uses a 16-bit cyclic redundancy check (CRC-16).

4.1.1.5 5-1.2 Exception Responses

If a Modbus master sends an invalid command to the SeaHawk 10K or attempts to read an

invalid register, an exception response is generated. The response packet will have the high

order bit of the function code set to one. The data field of the exception response contains the

exception error code.

Code

Name

Description

Illegal Function

The function code is not supported

Illegal Data Address

Attempt to access an invalid address

Illegal Data Value

Attempt to set a variable to an invalid value

Table 4.1

Exception Codes