PORTIBM PC Portable (uses same BIOS as XT) 217A-217B - ET4000/W32 CRTC-B/Sprite
Note:	Alternative addresses may depend on adapter manufacturer,
	  Tseng claims 21xA with x=three address bits, selected by IOD2..0
	  during power up reset.

21xA  RW  ET4000/W32(i) CRTC-B/Sprite index register
	bit7-0: index
21xB  RW  ET4000/W32(i) CRTC-B/Sprite data register (see #P1017)


(Table P1017)
Values for ET4000/W32(i) CRTC-B/Sprite data register index:
 E0h	CRTC-B / Sprite Horizontal PixelA picture element, the smallest addressable unit of a graphical display. Position, Low
	   bit7-0: horizontal pixel position bit7-0
 E1h	CRTC-B / Sprite Horizontal PixelA picture element, the smallest addressable unit of a graphical display. Position, High
	   bit7-4: reserved
	   bit3-0: horizontal pixel position bit11-8
 E2h	CRTC-B Width Low / Sprite Horizontal Preset
	   bit7-0: width of CRTC-B bit7-0
	   bit5-0: horizontal preset for sprite
 E3h	CRTC-B Width High / Sprite Horizontal Preset
	   bit7-4: reserved
	   bit3-0: width of CRTC-B bit11-8
 E4h	CRTC-B / Sprite Vertical PixelA picture element, the smallest addressable unit of a graphical display. Position, Low
	   bit7-0: vertical pixel position bit7-0
 E5h	CRTC-B / Sprite Vertical PixelA picture element, the smallest addressable unit of a graphical display. Position, High
	   bit7-4: reserved
	   bit3-0: vertical pixel position bit11-8
 E6h	CRTC-B Height Low / Sprite Vertical Preset
	   bit7-0: height of CRTC-B bit7-0
	   bit5-0: vertical preset for sprite
 E7h	CRTC-B Height High / Sprite Vertical Preset
	   bit7-4: reserved
	   bit3-0: height of CRTC-B bit11-8
 E8h	CRTC-B / Sprite Starting Address Low
	   pointer to CRTC-B / sprite image in display memory.
	   (maximum size of sprites 64x64x4=1KB with 4 colors:
	    00b=color-0, 01b=color-255, 10b=transparent, 11b=reserved)
	   bit7-0: startaddress bit7-0
 E9h	CRTC-B / Sprite Starting Address Middle
	   bit7-0: startaddress bit15-8
 EAh	CRTC-B / Sprite Starting Address High
	   bit7-4: reserved
	   bit3-0: startaddress bit19-16
 EBh	CRTC-B / Sprite Row Offset Low
	   bit7-0: offset bit7-0
 ECh	CRTC-B / Sprite Row Offset High
	   bit7-4: revision ID (any ET4000/W32)
		    0000b=W32	     0100b-1111b reserved
		    0001b=W32i
		    0010b=W32p
		    0011b=W32i, new
	   bit3-0: offset bit11-8
 EDh	CRTC-B PixelA picture element, the smallest addressable unit of a graphical display. Panning
	   bit7-3: reserved
	   bit2-0: CRTC-B pixel panning
 EEh	CRTC-B Color-Depth-Register / Hardware-Zoom
	   bit7-4: reserved (concerning databook ET4000/W32)
	   bit7-6: vertical zoom (undocumentedInformation about a product which is not publicly available from the manufacturer, and must be determined by reverse-engineering (disassembly, trial-and-error, etc.).	 Undocumented information tends to change -- often dramatically -- between successive revisions of a product, since the manufacturer has no obligation to maintain compatibility in behavior which is not explicitly stated.)
		   (original ET4000/W32 ok, doesn't work properly
		    with some ET4000/W32i)
		    00b=zoomx1	   10b=zoomx3
		    01b=zoomx2	   11b=zoomx4
	   bit5-4: horizontal zoom (undocumentedInformation about a product which is not publicly available from the manufacturer, and must be determined by reverse-engineering (disassembly, trial-and-error, etc.).	 Undocumented information tends to change -- often dramatically -- between successive revisions of a product, since the manufacturer has no obligation to maintain compatibility in behavior which is not explicitly stated.)
		   (original ET4000/W32 ok, doesn't work properly
		    with some ET4000/W32i)
		    00b=zoomx1	   10b=zoomx3
		    01b=zoomx2	   11b=zoomx4
	   bit3-0: bit/pixel
		    0000b=1	   0011b=8
		    0001b=2	   0100b=16
		    0010b=4
 EFh	CRTC-B / Sprite Control
	   bit7-2: reserved
	   bit1	 : 1=2nd CRTC-B image overlays main CRTC-A image
		   0=CRTC-B image at pin SP1/0
	   bit0	 : 1=enable CRTC-B
		   0=enable sprite (see F7h)
 F7h	Image Port Control
	   bit7	 : 1=CRTC-B or sprite active
		   0=CRTC-B and sprite not active
	   bit6-0: reserved