; Copyright 2006 Yamane Akira
SPITransfer:
      out USIDR,r16
      ldi r16,(1<<USIOIF)
      out USISR,r16
      ldi r16,(1<<USIWM0)|(1<<USICS1)|(1<<USICLK)|(1<<USITC)
SPITransfer_loop:
      out USICR,r16
      sbis USISR,USIOIF
      rjmp SPITransfer_loop
      in r16,USIDR
      ret