Request from Master to Slave
Range Byte
Slave address (1-255) 1
Function code (03-04) 1
Word starting address (high byte) 1
Word starting address (low byte) 1
Number of word (high byte) 1
Number of word (low byte) 1
Error check (CRC-16) (low byte) 1
Error check (CRC-16) (high byte) 1
Reply from Slave to Master
Range Byte
Slave address (1-255) 1
Function code (03-04) 1
Byte counter (n) 1
Data Error check (CRC-16) (low byte) 1
Error check (CRC-16) (high byte) 1
The “Data” field contains the requested words in the following format: high byte of the first word,
low byte of the first word, high byte of the second word, and so on. The “Data” field contains
8000h for not implemented addresses or for information not relevant in the actual device
configuration.
Example: Ask to slave at address 29 (1Dh) the value of 3 words (3h) starting from word 178
(B2h)
Reply from Slave to Master
Range Byte
Slave address 1Dh
Function code 03h
Byte counter 06h
Data FFh
Data 9Ch
Data 80h
Data 00h
Data 05h
Data 5Ah
Error check (CRC-16) (low byte) D7h
Error check (CRC-16) (high byte) 0Dh
To Next Page