Macro definition problem in W5500 library function

Question

Dear all I was confused when looking at the w5500 library function, as in the first picture, the w5500 Socket_n register corresponds to a 16-bit offset address. But in the actual library function, I see a 24-bit offset address as defined in the second diagram. Why add 08 at the end? And use the statement (ch<<5).Why not just define it as a 16-bit offset address according to the data manual? I will be very grateful if the Official technician will solve my confusion. 1806×1042 257 KB 21273×767 53.5 KB

Eugeny · Answer

This must be preparation of the 3rd byte in the SPI transaction. 0x08 is the socket 0 register set. If you add channel (socket) number shifted left by 5 bits you will get 16-bit address + bank identification for respective channel (socket) ready to shift to the SPI. The only additionally needed is set bit for write and 2 bits for transfer mode type.

Eugeny · Answer

You are looking into wrong place. Read the 2.2 of the datasheet, it will answer your question. 0x08 is bank (block) address of 0x01 shifted 3 bits left because lower 3 bits are occupied by other flags.

Bohu-Tang · Answer

Thanks a lot Eugeny. Your answer clears up my confusion.