sylvac PLC Mode D'emploi page 72

A.3.3 Frame example
To read the current position of an instrument whose slave address is 03, send it the following frame :
03 04 00 02 00 02 CRC16, where
03 : The SLAVE address of instrument
04 : The Read n Register command
00 02 : The address of the 1st register to be read
00 02 : The number of registers to read
The answer will be :
03 04 04 xx xx xx xx CRC16, where
03 : The SLAVE address of instrument
04 : The Read n Register command
04 : The number of read data bytes
xx xx xx xx : The 4 read bytes