RX Series SCI SPI Continuous Data Transmission Problem

CPU:RX23T

Implemented function: To control DAC7513 (16bit)through SCI SPI(8bit) , the timings to be implemented as below:

SCI SPI  16bit transfer by sending 2 data in succession, but there is always about 3us interval between the 2 bytes, how to remove this 3us interval?  Achieving continuous transmission of 2 bytes? Please ask the expert for guidance.

                    
   	sci_hdl_t sspiHandle;
	sci_err_t err;
    uint8_t sspi_buf[2];
    sci_cfg_t config;

//Initialize SCI
      config.sspi.spi_mode = SCI_SPI_MODE_1;/* SPMR Register CKPH=0, CKPOL=1 Mode 1: 01 CPOL=0 resting lo, CPHA=1 trailing edge/falling */
		config.sspi.bit_rate = 1000000; // 1 Mbps
		config.sspi.msb_first = true;
		config.sspi.invert_data = false;
		config.sspi.int_priority = 1;

		
		err = R_SCI_Open(SCI_CH1, SCI_MODE_SSPI, &config, NULL,
		&sspiHandle);
		R_SCI_PinSet_SCI1();
      
      
      
      
//send 2 bytes
             
                    SPI_CS  = CS_LOW;
		    	
		    	R_SCI_Send(sspiHandle, sspi_buf, 2);

		    		while (SCI1.SSR. BIT. TEND <1)
		    		{ }
		    	
		    		SPI_CS  = CS_HIGH;