Format of BBC Master control block for function FAh: Offset Size Description ) 00h BYTE number of parameters sent to I/O processor (0Dh,0Eh) 01h BYTE number of parameters read from I/O processor (01h) 02h DWORD I/O processor address 06h DWORD 80186 segment:offset address 0Ah WORD number of bytes to transfer 0Ch BYTE operation type 00h write to 65C12 at 24 us/byte 01h read from 65C12 at 24 us/byte 02h write to 65C12 at 26 us/word 03h read from 65C12 at 26 us/word 04h write to 65C12 at 10 us/byte using 256-byte blocks 05h read from 65C12 at 10 us/byte using 256-byte blocks 0Dh BYTE 65C12 memory access control (only used if offset 00h = 0Eh) (see #03212)