Commodore Amiga - Figure 3-11 Data Fetched for the Second Line When Modulo

Data for Line 2:
Location:
START+40
Leftmost
Display Word
START+42
Next Word
START+44
Next Word
START+78
Last Display
Word
Figure 3-11: Data Fetched for the Second Line When Modulo = 0
Note
that the pointers always contain an even number, because data is fetched from the
display a
word at a time.
There are two modulo registers-BPL1MOD for the odd-numbered bit-planes and
BPL2MOD for the even-numbered bit-planes.
The following example sets the modulo to 0 for a low-resolution playfield with one bit-
plane.
The bit-plane is odd-numbered.
BPL1MOD EQU $DFF108
jModulo Jor odd bit-planes
MOVE.W
#0,BPL1MOD
j8et modulo to 0
Data Fetch in High-resolution Mode
When you are using high-resolution mode to display the basic playfield, you need to
fetch 80 bytes for each line, instead of
40.
Modulo in Interlaced Mode
For interlaced mode, you must redefine the modulo, because interlaced mode uses two
separate scannings of the video screen for a single display of the playfield. During the
first scanning, the odd-numbered lines are fetched to the screenj and during the second
scanning, the even-numbered lines are fetched.
Playfield Hardware
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