Function 08H (Diagnostic With Sub-Function Code 00H); Broadcast Mode - CARLO GAVAZZI EM21 - COMMUNICATION PROTOCOL V1 REV0 Communication Protocol Manual

Energy management
Response frame (incorrect action)
Description
Physical address
Function code
Exception code
CRC
1.2.4

Function 08h (Diagnostic with sub-function code 00h)

MODBUS function 08h provides a series of tests to check the communication system between a client
(Master) device and a server (Slave), or to check various internal error conditions in a server.
EM24-DIN supports only 0000h sub-function code (Return Query Data). With this sub-function the data
passed in the request data field is to be returned (looped back) in the response. The entire response
message should be identical to the request.
Request frame
Description
Physical address
Function code
Sub-function
Data (N word)
CRC
Response frame (correct action)
Description
Physical address
Function code
Sub-function
Data (N word)
CRC
Response frame (incorrect action)
Description
Physical address
Function code
Exception code
CRC
1.2.5

Broadcast mode

In broadcast mode the master can send a request (command) to all the slaves. No response is returned
to broadcast requests sent by the master. It is possible to send the broadcast message only with
function code 06h using address 00h.
EM24-DIN Communication Protocol
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 86h
1 byte 01h, 02h, 03h, 04h
2 bytes
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 08h
2 bytes 0000h
N *2 bytes Data
2 bytes
Length Value
1 byte 1 to F7 (1 to 247)
1 byte 08h
2 bytes 0000h
N *2 bytes Data
2 bytes
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 88h
1 byte 01h, 02h, 03h, 04h
2 bytes
Note
Possible exception :
01h: illegal function
02h: illegal data address
03h: illegal data value
04h: slave device failure
Note
Byte order: MSB, LSB
Note
Byte order: MSB, LSB
Note
Possible exception :
01h: illegal function
02h: illegal data address
03h: illegal data value
04h: slave device failure
5