T
+
4
*
6
- timing cycle -
+
2
3
*
5
Figure
6-13:
Time Slots Used by a Six-bit-plane Display
Notes for figure 6-13:
+ an open memory slot
that
the 68000 might use
T+7
I
1
* a slot
that
cannot be used by the 68000 because of added bit-plane DMA
If
you specify four high-resolution bit-planes (640 pixels wide), bit-plane DMA needs
all
of the available memory time slots during the display time
just
to
fetch the
40
data
words for each line of the four bit-planes (40 x 4 = 160 time slots). This effectively
locks
out
the 68000 (as well as the blitter or Copper) from any memory access during the
display.
Figure 6-14 shows how the time slots are allocated for high-resolution bit-planes.
T
- timing
cycle-
T+7
4
2 3
1
4 2
3
Figure
6-14:
Time Slots Used by a High-resolution Display
19O
Blitter Hardware
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