How to parse DI return instructions

　　Demonstrate with DAM0404 instruction

　　Query optocoupler (4-way optocoupler)

　　Send command code: FE 02 00 00 00 04 6D C6

　　Optocoupler return information:

　　Return code: FE 02 01 00 91 9C

　　For example, the return command query status is FE 02 01 03 D1 9D

　　FE is the device address, 02 is the query command, 01 is the number of bytes returned, 03 is the current state, and the last is the check digit.

　　03 is the current state:

　　03 is hexadecimal data and needs to be converted to binary as 0011

　　The state needs to be viewed from right to left,

　　0 0 1 1

　　That is, the first channel and the second channel are currently open.