Format of TI Professional System ROM data area:
Offset	Size	Description	)
 00h	BYTE	port 00h shadow
 01h	BYTE	port 03h shadow
 02h	BYTE	port 04h shadow
 03h	WORD	system configuration word (see #03266)
 05h	BYTE	25ms count
 06h	WORD	offset of timing event 1 (0008h)
 08h	WORD	(event 1) offset of timing event 2 (0010h)
 0Ah	BYTE	(event 1) unused (FFh)
 0Bh	BYTE	(event 1) active flag (bit 7 set if on)
 0Ch	WORD	(event 1) count-down until end of event
 0Eh	WORD	(event 1) event routine (in segment F400h) to call at timeout
 10h	WORD	(event 2) offset of timing event 3 (0018h)
 12h	BYTE	(event 2) unused (FFh)
 13h	BYTE	(event 2) active flag (bit 7 set if on)
 14h	WORD	(event 2) count-down until end of event
 16h	WORD	(event 2) event routine (in segment F400h) to call at timeout
 18h	WORD	(event 3) offset of timing event 3 (0020h)
 1Ah	BYTE	(event 3) unused (FFh)
 1Bh	BYTE	(event 3) active flag (bit 7 set if on)
 1Ch	WORD	(event 3) count-down until end of event
 1Eh	WORD	(event 3) event routine (in segment F400h) to call at timeout
 20h	WORD	(event 4) 0000h - last event
 22h	BYTE	(event 4) unused (FFh)
 23h	BYTE	(event 4) active flag (bit 7 set if on)
 24h	WORD	(event 4) count-down until end of event
 26h	WORD	(event 4) event routine (in segment F400h) to call at timeout
 28h	WORD	offset of start of text display within segment DE00h
 2Ah	WORD	end of display
 2Ch	WORD	current absolute cursor position
 2Eh	WORD	start of current character row
 30h	WORD	current cursor column
 32h	WORD	cursor type and size (see #03264)
 34h	WORD	start of protected status region on screen (0000h = none)
 36h	BYTE	pop flag used by some ROM routines
		00h pop registers before return
		nonzero: do not pop
 37h	BYTE	unused (FFh)
 38h	BYTE	PAUSE flag
		00h off
		FFh on
 39h	BYTE	temp: current attribute while moving characters on screen
 3Ah	WORD	start of keyboard queue (next key at start+2 or 0042h if 0060h)
 3Ch	WORD	end of keyboard queue (next key inserted at end+2 or 0042h)
 3Eh	BYTE	number of characters in buffer
 3Fh	BYTE	keyboard mode flags (see #03265)
 40h	BYTE	Alt-digit-digit-digit accumulator
 41h	BYTE	Alt-digit-digit-digit count of digits (mod 3)
 42h 16 WORDs	keyboard buffer (circular queue)
 62h  8 DWORDs	Drive Interface Table pointers for floppies A:-D: + four others
		(0000h:0000h if pointer not in use)
 82h	BYTE	disk-error retry count (incremented on each disk error)
 83h  2	BYTEs	BIOS scratch space
 85h  8 BYTEs	current cylinder number for drives 0-7
		FFh = unknown
 8Dh	BYTE	BIOS scratch space
 8Eh	BYTE	hard error code for last disk access
		00h operation successful
 8Fh  8 BYTEs	save area for disk DSR parameters
 97h  6 BYTEs	current drive status
 9Dh	BYTE	retry error status
 9Eh	BYTE	BIOS scratch space
 9Fh  7 BYTEs	???
 A6h  2	WORDs	INT 47 save area for SS,SP
 AAh  2	WORDs	INT 46 save area for SS,SP
 AEh  2	WORDs	INT 43 save area for SS,SP
 B2h  2	WORDs	save area for SS,SP to be restored by common intr. exit routine
 B6h 24 WORDs	stack for INT 47
 E6h 24 WORDs	stack for INT 46
116h 17 WORDs	stack for INT 43
13Ah  6 BYTEs	system date and time (hundredths, seconds, minutes, hours, and
		  WORD days since 01jan1980)
Note:	timing event 1 is the disk I/O timeout, event 2 is the floppy disk
	  motor timeout, event 3 is the floppy disk motor spin-up time, and
	  event 4 is used to turn off the speaker after a delay