freemodbus从机问题，一直断言在assert( eRcvState == STATE_RX_IDLE )？

BOOL
xMBRTUTransmitFSM( void )
{
    BOOL            xNeedPoll = FALSE;
  **  assert( eRcvState == STATE_RX_IDLE );//通过测试，每次都断言在这个地方
    switch ( eSndState )
    {
        /* We should not get a transmitter event if the transmitter is in
         * idle state.  */