From SpecNext official Wiki
|Short desc.||Sends byte to serial port. If read, tells if data in RX buffer|
|Bit Mask||%0001 0011 0011 1011|
- send a byte to the connected device. There is no Tx buffer so the program must make sure the last transmission is completed before sending another byte.
- bit 2 = 1 if the read buffer is full
- bit 1 = 1 if the transmitter is busy sending a byte
- bit 0 = 1 if the read buffer contains received bytes