When an AVR is run as an SPI slave and it recieves a data byte, the data byte is...
(I've read each of these)
- copied from the shift register to the data register
- transfered from the shift register to the data register
- moved from the shift register to the data register
My question is, does the shift register retain a copy of the byte recieved or is the shift register cleared by this (copy / transfer / move) to SPDR? I am wanting a data byte sent by the master to be echoed back on the next byte transfer. I don't know if the slave needs to write the byte back to SPDR or if the shift register retains the master's sent data byte.