问如何编写通过SPI Master从内存传输数据到2个slave的代码

EN

    if ( (SWITCHPORTL.IN & PIN1_bm) == 0 )
    {
        j = 0;
        while (j < NUM_BYTES)
        {
            // Wait till there is unread data in the receive buffer
            while((USART.STATUS & USART_RXCIF_bm) == 0 ){};
            // Read out the received data
            __far_mem_write(j+SDRAM_ADDR, USART.DATA);
            if (j == (NUM_BYTES-1))
            {
                // Toggle LED 1
                LEDPORT.OUTTGL = PIN1_bm;
            }
            j++;
        }
    }