CARLO GAVAZZI EM 21, Руководство по протоколу связи

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Energy management
EM24-DIN Communication Protocol
5
Response frame (incorrect action)
Description Length Value Note
Physical address 1 byte 1 to F7h (1 to 247)
Function code 1 byte 86h
Exception code 1 byte 01h, 02h, 03h, 04h
CRC 2 bytes
Possible exception :
01h: illegal function
02h: illegal data address
03h: illegal data value
04h: slave device failure
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 Length Value Note
Physical address 1 byte 1 to F7h (1 to 247)
Function code 1 byte 08h
Sub-function 2 bytes 0000h
Data ( N word) N *2 bytes Data Byte order: MSB, LSB
CRC 2 bytes
Response frame (correct action)
Description Length Value Note
Physical address 1 byte 1 to F7 (1 to 247)
Function code 1 byte 08h
Sub-function 2 bytes 0000h
Data ( N word) N *2 bytes Data Byte order: MSB, LSB
CRC 2 bytes
Response frame (incorrect action)
Description Length Value Note
Physical address 1 byte 1 to F7h (1 to 247)
Function code 1 byte 88h
Exception code 1 byte 01h, 02h, 03h, 04h
CRC 2 bytes
Possible exception :
01h: illegal function
02h: illegal data address
03h: illegal data value
04h: slave device failure
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.