Modbus Registers OPTIMA...GOMOD

Short instruction 227VM-024-05-MB
Written by: Michael Köhle Date: 13.11.2014 08:56:00 Side 12 of 13
2.1.6. Error handling
If the server receives the request, but detects a communication error (parity, LRC,
CRC, wrong address...), no response is returned. The client program will eventually pro-
cess a timeout condition for the request.
If the server receives the request without a communication error, but cannot handle it
(for example, if he request is to read a non–existent register), the server
will return an exception response informing the client of the nature of the error.
Device response:
Ad-
dress
Function
code +80h
Error
code
CRC End
1 byte 1 byte 1 byte 2byte(CRC_Lbyte, CRC_Hbyte) 3,5 Chars
Error code Name Description
01h Illegal function The function code received in the query is not
an allowable action.
02h Illegal data address The data address received in the query is not
an allowable register address.
Register address are read only.
03h Illegal data value A value contained in the query data field is not
an allowable value.
Wrong number of registers.
Register address are read only.
06h Slave device busy Specialized use in conjunction with program-
ming commands. The server (or slave) is en-
gaged in processing a long–duration program
command.