INT 4A - Acorn BBC Master 512 - "OSWORD" - MISC FUNCTIONS USING CONTROL BLOCK
	AL = function code
	    FAh transfer data between 80186 and 65C12 I/O processor
	DS:BX -> control block (see #03211)
Return: FLAGS destroyed
	control block updated
Note:	there are more functions than are listed here, but details are not
	  available
SeeAlso: INT 40"Acorn",INT 4B"Acorn",INT 4C"Acorn"


Format of BBC Master control block for function FAh:
Offset	Size	Description	(Table 03211)
 00h	BYTE	number of parameters sent to I/O processor (0Dh,0Eh)
 01h	BYTE	number of parameters read from I/O processor (01h)
 02h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	I/O processor address
 06h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	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)


Bitfields for 65C12 memory access control:
Bit(s)	Description	(Table 03212)
 7	unused
 6	always use main screen memory if I/O addr 3000h-7FFFh (overrides bit 5)
 5	use shadow screen memory if screen address specified
 4	use current ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. rather than ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. selected by bits 3-0 (only if I/O
	  address between 8000h and BFFFh)
 3-0	paged ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. number