CARLO GAVAZZI EM 21, Communication Protocol Manual

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Energy management
EM24-DIN Communication Protocol
4
Response frame (incorrect action)
Description Length Value Note
Physical address 1 byte 1 to F7h (1 to 247)
Function code 1 byte 83h
Exception code 1 byte 01h, 02h, 03h, 04h (see note)
CRC 2 bytes
Possible exception :
01h: illegal function
02h: illegal data address
03h: illegal data value
04h: slave device failure
1.2.2 Function 04h (Read Input Registers)
This function code is used to read the contents of a contiguous block of input registers (word). The
Request frame specifies the starting register address and the number of registers to be read. It is
possible to read maximum 11 register (word) with a single request, when not differently specified.
The register data in the response message are packed as two bytes per register (word), with the binary
contents right justified within each byte. For each register, the first byte contains the high order bits
(MSB) and the second contains the low order bits (LSB).
Request frame
Description Length Value Note
Physical address 1 byte 1 to F7h (1 to 247)
Function code 1 byte 04h
Starting address 2 bytes 0000h to FFFFh Byte order: MSB, LSB
Quantity of registers ( N word) 2 bytes 1 to 10h (1 to 11) Byte order: MSB, LSB
CRC 2 bytes
Response frame (correct action)
Description Length Value Note
Physical address 1 byte 1 to F7h (1 to 247)
Function code 1 byte 04h
Quantity of requested bytes 1 byte N word * 2
Register value N *2 bytes 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 84h
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
1.2.3 Function 06h (Write Single Holding Register)
This function code is used to write a single holding register. The Request frame specifies the address of
the register (word) to be written and its content.
The correct response is an echo of the request, returned after the register content has been written.
Request frame
Description Length Value Note
Physical address 1 byte 1 to F7h (1 to 247)
Function code 1 byte 06h
Starting address 2 bytes 0000h to FFFFh Byte order: MSB, LSB
Register value 2 bytes 0000h to FFFFh Byte order: MSB, LSB
CRC 2 bytes
Response frame (correct action)
Description Length Value Note
Physical address 1 byte 1 to F7h (1 to 247)
Function code 1 byte 06h
Starting address 2 bytes 0000h to FFFFh Byte order: MSB, LSB
Register value 2 bytes 0000h to FFFFh Byte order: MSB, LSB
CRC 2 bytes