Function 04H (Read Input Registers); Function 06H (Write Single Holding Register) - CARLO GAVAZZI EM21 - COMMUNICATION PROTOCOL V1 REV0 Communication Protocol Manual

Energy management
Response frame (incorrect action)
Description
Physical address
Function code
Exception code
CRC
1.2.2

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
Physical address
Function code
Starting address
Quantity of registers (N word)
CRC
Response frame (correct action)
Description
Physical address
Function code
Quantity of requested bytes
Register value
CRC
Response frame (incorrect action)
Description
Physical address
Function code
Exception code
CRC
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
Physical address
Function code
Starting address
Register value
CRC
Response frame (correct action)
Description
Physical address
Function code
Starting address
Register value
CRC
EM24-DIN Communication Protocol
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 83h
1 byte 01h, 02h, 03h, 04h (see note)
2 bytes
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 04h
2 bytes 0000h to FFFFh
2 bytes 1 to 10h (1 to 11)
2 bytes
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 04h
1 byte N word * 2
N*2 bytes
2 bytes
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 84h
1 byte 01h, 02h, 03h, 04h
2 bytes
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 06h
2 bytes 0000h to FFFFh
2 bytes 0000h to FFFFh
2 bytes
Length Value
1 byte 1 to F7h (1 to 247)
1 byte 06h
2 bytes 0000h to FFFFh
2 bytes 0000h to FFFFh
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
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
Note
Byte order: MSB, LSB
Byte order: MSB, LSB
Note
Byte order: MSB, LSB
Byte order: MSB, LSB
4