Bitfields for PC-MOS/386 serial port protocol:
Bit(s)	Description	)
 7	set to enable/disable CD monitoring, clear to set protocol
---bit 7 set---
 4	CD monitoring enabled
 5	automatic restart enabled
---bit 7 clear---
 0	receive XON/XOFF
 1	transmit XON/XOFF
 2	DTR/DSR
 3	RTS/CTS