the first Mode line and is also used as the scan line number to end the display in the last Mode line (the line without the VS bit set). Example: Given an eight scan line ANTIC Mode (Text Modes 2, 4, or 6) with the VS bit set on two adjacent Mode lines the scrolling region then consists of three Mode lines—the third line in the scrolling region is the first Mode line encountered without the VS bit set. When Vertical scrolling is not set in the Display List the three Modes lines would naturally result in 24 displayed scan lines. When the VS bits are set in the Display List Mode instructions as described and the VSCROL value is set to 2 then the first Mode line in the region begins displaying at scan line 2 showing scan lines 2 to 7 (six scan lines or 8 - VSCROL), the second Mode line is displayed completely (eight scan lines), and the final Mode line ends at scan line 2 showing scan lines 0 to 2 (three scan lines or VSCROL + 1). The total scan lines displayed in the scrolling region is then 6 + 8 + 3 = 17 scan lines. Since fine scrolling is based on scan lines not pixel height, and scrolling region movement is done simply by skipping scan lines from the first Mode line and adding scan lines to the last Mode line, it is possible to use different graphics Modes within the scrolling region. This merely requires additional care when determining how many scan lines can be shifted for the current first and last Mode lines in the scrolling region. Blank Mode lines cannot be contained within a scrolling region, because Blank Mode line instructions inherently do not have a Vertical Scroll Modifier bit. (Blank Mode line instructions specify the blank line count using the bits 7 through 5 that function as LMS, HS, and VS Modifiers for "regular" Playfield Mode instructions.) However, a Blank Mode instruction can be used to end a scrolling region and is still subject to the expected scan line height changes per the vertical scroll value. PMBASE $D407 Write Player Missile Base Address This specifies the page of the base address for Player/Missile graphics. When double line resolution P/M graphics are operating the PMBASE value must begin on a 1K boundary. When single line resolution P/M graphics are