Atari 400 Technical Reference Manual page 528

Mixing Graphics Modes, cont.
II. PROCEDURE TO SET UP SCREEN IN MIXED MODES:
1. Select modes desired, then look up which mode is the max
RAM mode from table #2.
example: modes selected - mode 1, mode 7, mode 2
mode 7
=
max RAM mode
2. Use table #1 to calculate the number of mode lines such
that the total number of scan lines
=
192.
example: scan
lines
II
mode per scan
mode line mode lines
line
1
6 8 48
7 56 2 112
2 2 16
32
192 TOTAL
3. If the max RAM mode is at the top of the screen, then skip
this step: Calculate the LMS byte by setting the left
nibble to 4, then use table #1 to find the right nibble for
the graphics mode at the top of the screen.
example: 1. left nibble
=
4
2. right nibble for mode 1 6
3. LMS byte
=
46 (HEX)
4. Calculate the mode byte for each mode. Set the left nibble
to 0, use table #1 to find the right nibble for each mode.
example:
I
Left
I
Rightl Hode
Model Nibblel Nibblel
Byte
I I I
(HEX)
I I I
1
I
0
I
6
I
06
7
I
0
I
D
I OD
2
I
0
I
7
I
07
B
-3-