I have an electronics board that uses an ATmega324PB microcontroller that uses SPI communications to communicate with another device on the board.
In a coding function that reads a register through SPI communications, there is a transmission of "0xAA". The application note (excerpt below) regarding SPI communications mentions something, but it implies some kind of check required, which doesn't seem to match what the code is doing.
If I removed that "SPI transmission of 0xAA" line, the function does not work correctly.
Is there a better explanation of what 0xAA does in terms of reading from a register via SPI with the ATmega324PB microcontroller?