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.