1 Enables the modifier, and 0 disables the modifier. Bit 4 - $10hex/16dec Horizontal Scroll. Bit 5 - $20hex/32dec Vertical Scroll. Bit 6 - $40hex/64dec Load Memory Scan. Bit 7 - $80hex/128dec Display List Interrupt. HS Modifer - Horizontal Fine Scroll Bit4: position value $10, controls horizontal scrolling of the playfield mode. When horizontal scrolling is enabled ANTIC retrieves more screen memory bytes than displayed in order to show partially scrolled display bytes at the beginning and end of the line. If the display is in Narrow mode ANTIC retrieves the number of screen bytes necessary for Normal mode. If the display is in Normal mode ANTIC retrieves the number of bytes needed for Wide screen mode. In Wide screen mode ANTIC does not retrieve any additional screen bytes. Scrolling in Wide screen will cause blank data to be shifted into the scrolled area. This is not a problem, because it occurs in the overscan area which is not visible on a normal NTSC/PAL display. VS Modifer - Vertical Fine Scroll Bit5: position value $20, controls vertical scrolling of the Playfield mode. The Vertical scrolling region in a display is defined by setting the VS bit ($20) on a sequential series of ANTIC Mode Lines in the Display List. The first Mode line without the VS bit set becomes the end of the scrolling region and is used as a buffer line to supply the new information to scroll up into the bottom of the scrolling region. LMS Modifer - Load Memory Scan Bit6: position value $40, loads a new address for the start of screen memory for the current Playfield mode line. The LMS option loads ANTIC's screen memory scan address with the 16-bit value in the two bytes following the instruction. The Character or Map mode specified will begin displaying bytes from that address. The LMS option must appear in the first Playfield Mode Instruction line (not Blank Line) in the Display List to initialize ANTIC to begin reading at the start of screen memory. Most of the Operating System-generated full screen modes will have only that one occurrence of the LMS modifier present in the Display List. ANTIC will automatically increment its LMS address at the end of each mode line in preparation for the next line. As long as screen memory does not cross over a 4K boundary the LMS modifier is not needed on subsequent