我向28335 SCI发数的时候为什么会回显发过去的字符串？

如题，我用串口助手向28335的SCIC发数，然后28335会把接收到的数据回显出来。但是我没有设置它回显啊？

我特意将28335的TXENA去掉了，可是28335还是会把数回显出来。

附上配置代码：

void scic_init()
{
ScicRegs.SCIFFTX.all = 0x8000;

ScicRegs.SCICCR.all = 0x0007; // 1 stop bit, No loopback
// No parity,8 char bits,
// async mode, idle-line protocol
ScicRegs.SCIHBAUD = 0x0000;
ScicRegs.SCILBAUD = 0x00F3; //19200 bps

ScicRegs.SCICTL2.bit.RXBKINTENA = 1;
ScicRegs.SCICTL1.all = 0x0021; // Relinquish SCI from Reset
}

void main(void)
{
float measure;

InitSysCtrl();
InitScicGpio();
InitPieCtrl();
IER = 0x0000;
IFR = 0x0000;
InitPieVectTable();

EALLOW;
PieVectTable.SCIRXINTC = &rxcint_isr;
scic_init();
EDIS;

PieCtrlRegs.PIEIER8.bit.INTx5 = 1; // Enable all SCIA RXINT interrupt
IER |= M_INT8; // enable PIEIER9, and INT9
EINT;

while(1)
  {
  if(sb_ack)
    {
      measure = Str2Num(stringbuffer);
      sb_ack = 0;
    } 
  }

}