Playfield Mode Instructions. Full screen displays using Playfield Map Modes E or F will have a second occurrence of the LMS modifier on a Map Instruction near the middle of the screen, since the full display requires more than 4K of screen memory. (Mode F displays include high res 320 pixel lines, and the GTIA display modes.) Combining the Map and Character Mode instructions with the LMS bit makes it possible to set the screen memory address freely within the 64K address space independently for each display line. In other words, the screen memory does not have to be completely contiguous memory scanned sequentially towards higher addresses - only that a single Mode line must be provided with adequate sequential bytes of memory to meet the requirements of that Mode, width of the display, and Scrolling feature. DLI Modifer - Display List Interrupt Bit7: position value , directs ANTIC to invoke a CPU-serviced interrupt on the last scan line of the Playfield Mode. If ANTIC register NMIEN (hex/54286dec) has Bit7 () set then on the last scanline of the Mode line an interrupt routine will be triggered which is vectored through address VDSLST (200hex/512dec). The 6502 Accumulator, X and Y register contents are not preserved before entry to the DLI routine. It is the responsibility of the DLI routine to save the state of the registers used during the DLI, and then restore the original values of the registers before exiting with an RTI instruction. Routines typically push the register values to the 6502 stack. DLI routines are ordinarily short and quick, changing the color registers or Player-Missile positions before exiting. However, brevity is not required. As long as the DLI routine exits before the start of the next DLI routine the DLI routine can continue updating values across multiple scanlines. Playfield Graphics Modes The ANTIC chip allows a variety of different Playfield modes and widths. However, the original Atari Operating System included with the Atari 800/400 computers provides easy access to a limited subset of these graphics modes. ANTIC Playfield modes are exposed to users through Atari BASIC via the "GRAPHICS" command, and to some other languages, via similar system calls. Oddly, the modes not directly supported by the original OS and BASIC are modes most useful for games. The later version of the OS used in the Atari 8-bit XL/XE computers added support for most of these "missing"