The steps for defining a basic playfield are summarized below: 1. Define Playfield Characteristics -------------------------------- a. specify color for each pixel: * Load desired colors in color table registers. * Define color of each pixel in terms of the binary value that points at the desired color register. * Build bitplanes and set bitplane registers: Bits 12-14 in bplcon0 - number of bitplanes ( bpu2 - bpu0 ). bplxpth - pointer to bitplane starting position in memory (written as a long word). b. specify resolution : * Low resolution: 320 pixels in each horizontal line. Clear bit 15 in register bplcon0 ( hires ). * High resolution: 640 pixels in each horizontal line. Set bit 15 in register bplcon0 ( hires ). c. specify interlaced or non-interlaced mode : * Interlaced mode: 400 vertical lines for NTSC, 512 for PAL. Set bit 2 in register bplcon0 ( lace ). * Non-interlaced mode: 200 vertical lines for NTSC, 256 for PAL. Clear bit 2 in bplcon0 ( lace ). 2. allocate memory . to calculate data-bytes in the total bitplanes, ----------------- use the following formula: Bytes per line * lines in playfield * number of bitplanes 3. define size of display window . ------------------------------- * Write start position of display window in diwstrt : Horizontal position in bits 0 through 7 (low order bits). Vertical position in bits 8 through 15 (high order bits). * Write stop position of display window in diwstop : Horizontal position in bits 0 through 7. Vertical position in bits 8 through 15. 4. define data fetch . set registers ddfstrt and ddfstop : ------------------- * For ddfstrt , use the horizontal position as shown in setting the display window starting position . * For ddfstop , use the horizontal position as shown in setting the display window stopping position . 5. define modulo . set registers bpl1mod and bpl2mod . set modulo to 0 --------------- for non-interlaced, 40 for interlaced. 6. Write Copper Instructions To Handle redisplay . ----------------------------------------------- 7. enable color display .for the a1000: set bit 9 in bplcon0 to enable the ---------------------- the color display on a composite video monitor. RGB video is not affected. Only the A1000 has color composite video output, other Amiga models cannot enable this feature using standard hardware.