Datasheet

184
ATmega325/3250/645/6450
2570K–AVR–04/07
ret
The code is size optimized using only eight instructions (+ ret). The code example
assumes that the DO and USCK pins are enabled as output in the DDRE Register. The
value stored in register r16 prior to the function is called is transferred to the Slave
device, and when the transfer is completed the data received from the Slave is stored
back into the r16 Register.
The second and third instructions clears the USI Counter Overflow Flag and the USI
counter value. The fourth and fifth instruction set Three-wire mode, positive edge Shift
Register clock, count at USITC strobe, and toggle USCK. The loop is repeated 16 times.