     PAL-Timing scheme for a bad scan line, no sprites:

      +---------------------------------------------------------------+
      |         1         2         3         4         5         6   |
      |123456789012345678901234567890123456789012345678901234567890123|Cycles
      +---------[------(--------------------------------------)---]---+Borders
      |3-4-5-6-7-rrrrrgggggggggggggggggggggggggggggggggggggggg--0-1-2-|Phi-1 VIC
      |              cccccccccccccccccccccccccccccccccccccccc         |Phi-2 VIC
      |xxxxxxxxxxxXXX========================================xxxxxxxxx|Phi-2 CPU
      +---------------------------------------------------------------+

      "-" = idle bus cycle (reads from the last byte of the video bank)

       <num> = pointer fetch for sprite <num>  ;  g = graphics fetch
       r = memory refresh cycle  ;  c = character pointer and/or color data fetch

       x  = processor executes instructions (BA high, AEC high)
       X  = bus request pending, bus still available (BA low, AEC high);
            processor may execute write cycles, stops on the next read cycle.
      "=" = bus unavailable (BA low, AEC low); processor is blocked because it
            would like to read something.