The serial device operates like the other Amiga devices. To use it, you must first open the serial device, then send I/O requests to it, and then close it when finished. See the "Introduction to Amiga System Devices" chapter for general information on device usage. The I/O request used by the serial device is called IOExtSer. struct IOExtSer { struct IOStdReq IOSer; ULONG io_CtlChar; /* control characters */ ULONG io_RBufLen; /* length in bytes of serial read buffer */ ULONG io_ExtFlags; /* additional serial flags */ ULONG io_Baud; /* baud rate */ ULONG io_BrkTime; /* duration of break in microseconds */ struct iOTArray io_TermArray; /* termination character array */ UBYTE io_ReadLen; /* number of bits per read character */ UBYTE io_WriteLen; /* number of bits per write character */ UBYTE io_StopBits; /* number of stopbits for read */ UBYTE io_SerFlags; /* serial device flags */ UWORD io_Status; /* status of serial port and lines */ }; See the include file devices/serial.h for the complete structure definition. Opening The Serial Device Writing To The Serial Device Reading From The Serial Device Closing The Serial Device