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Register Functions - Sharp MZ-800 Service Manual

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4-2-7. Register functions
VRAM configuration
• One or two chips of 16 KB VRAM are used.
• In the case of a single 16 KB VRAM chip, it handles
320
x
200 dots, 4 colors, or 640
x
200 dots 1 color.
• In the case of two 16 KB VRAM chips, it handles 320
x
200 dots, 16 colors, 640
x
200 dots, 4 colors, 320
x
200 dots, 4 colors, 2 frames, or 640
x
200 dots, 1
color, two frames.
*
Discussed next are about functions of the custom LSI.
There may be some restrictions because the standard
version of the MZ-800 incorporates only one 16 KB
RAM.
Display mode register (OUT &HCE)
• It consists of four bits which are used to represent
display method, resolution, and display screen (color
plane) in combined way.
Display mode register (DMD)
MZ-800
• DMD 3, 2: Display method and resolution
DMD
3
o
2
o
Bit map, 320 x 200
o
I
1
I
Bit map,
64~~
_____ _
1
-i
0
I
MZ-700 mode
-----~--
----------------+------------------------~~-----
1
1
I
Prohibited
• DMD 1, 0: Display screen designation
DMD DMD
320
x
200
640
x
200
I
MZ-700
1
0
-~=
0
0
Frame A, Planes I and
n
Frame A, Plane I
Normal
0
1
Frame B, Planes ID and IV
Frame B, Plane ID (NOTE)
Prohibited
1
0
Planes I,
n, m,
and IV
Planes I,
m
I
Prohibited
1
1
Prohibited
NOTE: 640 x 200, Plane B
IS
Plane
m,
not Plane
n.
• With the MZ-800, DMD 1
~
0, DMD 0
=
O.
Table-' VRAM configuration and display mode
VRAM
I
Display
Display
Color combination
DMD
VRAM configuration
Resolution
~:~~c~
_________
~
___ . .
~_~______
i
0010'
'"me
(NOTEI
_ _
3
2
__
'I
0
_I : ItIVTI'
1
320
x
200
140010<5,
F"mJ
I.
n
I
0
0
1
0
I
0
16 KB
8000
H
f - - - -
~
___
~ _ B _ F _ F _ F
-VA-0--7
--vc-o-.,
-----llltl
I
F"me
+
n
l~
-
~o 1~+-;
""'" I
I
11
j
r-Ll
320
x
200
140010<5
(eme
B
1
rn,
;---1
~-i -~
l
0
+r~-
H
G G G
-t-------+--~t-
-- ---
32
KB _ _
-=-~
"
on
"
1' 6
0010<5
I
F"me
~I. ~~-f
I
0
_1_'
r
T' vcr
~010' l:am~-____f--~---1-l-~~---~-
8000
0
G
t
640 x 200
i
I-~ame
B
I
ill
I
0
i
1
I
0
i , l
1
[
1
i
I
!
i
I
III
I
1--------
I
---1---1-----+----
I
I
I
I
BFFF
+.1.
4 colors Frame A
I I.
ill
i
0
i
1
i
1
i
0
!
+----:-
I
!
I
:
~-~-- --------------~~---------~
I
~0-2-c5-h-~r-nae-cs-te-r-s-t-II-8
0010<5
!"me
A
I
AGB
I,
fo
T~
i;-
640
x
200
(NOTE) Except for the MZ-700 mode, actual display colors are produced by the pallet.
20

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