PAL-Timing scheme for a normal scan line, no sprites on the current scan line
 but at least the sprites 1+2 active on the following scan line:

  |         1         2         3         4         5         6   |
  |3-4-5-6-7-rrrrrgggggggggggggggggggggggggggggggggggggggg-N0-1s2s|Phi-1 VIC
  |                                                           ssss|Phi-2 VIC
  |xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxXXX====|Phi-2 CPU

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

   <num> = pointer fetch for sprite <num>  ;  g = graphics fetch
   s = sprite data fetch  ;  r = memory refresh cycles
   N = extra '-' cycles for NTSC added here

   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.