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Sharp MZ-800 Service Manual page 25

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c) Example of CPU read/write access
• Shown next are access examples of REPLACE write,
PS ET write, and SEARCH read in the 320 x 200,
16-color mode.
As for display colors, Plane I corresponds to 8, IT to
R, ill to G, and IV to I.
MZ-800
CD
REPLACE write
• To develop light yellow characters on the graphic
screen.
Plane I (B) data
Plane 11 (R) data
V
Bo
1
0 1 ° 1'1'1'1'
i
COTo
i
'1'
1
°R~
R
Display before write
A
M
Plane III (G) data
It develops the screen when a next CG patterns are
written after setting the REPLACE mode and the light
yellow color in the WF register.
Mode
BlA Calor designation
WF register
~-O--o=r!]
,
,
--oJ:
Light yellow replace mode
Plane I
So, the bit "1" of the write data becomes the color
specified by WF and rest of others become RESET
(black).
°
Write data
I
(CG pattern) ,
°
~-----
Plane 11
°
V
I
° 1
°lolol~liEJ
10t'lol'[0]
, !
° I' I
R
A
M
Plane III
Plane IV
Display after write
1 °
I ,
1 °
I' I
°
1 ' 1
°
liJ
1 °
I' 1
°
1
' 1 °
I'
1 ON
®
PSET write
• To overlay a light yellow hatching over the graphic
display screen of
CD.
Mode
BlA Calor designation
WF register
' - - 1 _, ___ 0- - - ' 1 _0- - - - ' - 1 _, _____ 0_1 :
Light yellow PSET mode
G
R
B
Write data
~
°
°
I (B)
11 (RI
° 1 ° 1 ° 1 ° I' 1 ° 1 ' 1 ° I I ° 1 ' I' I' 1 ° I' I' I, 1
V
R
A
Display after write
M
1 ° I' I'
So, only the bit "1" of the write data becomes the
color specified by WF in this mode, and rest of other
colors do not change.
@ SEARCH read
+
PS ET write
• To change light yellow in
®
above to change to red
• The following data are set when the memory is read
after setting the light yellow search mode in the RF
register.
Mode
BlA Calor designation
RF register
LI_,_IL-_----' - I_o_--' - I_, ____ o---' I :
Light yellow search
III (GI
IV(!)
I'
24
I'
I' 1
°
I'
1 ° I'
1
°
1 ' 1
°
I'
1
0
I'
1
Read data
1 °
°
°
0' I:
Only the bit of light yellow
L . -_ _ _ _ _ _ _ _ _ _ --'
becomes ",",
• When the above read data are read after setting the
red PSET mode in the WR register.
...
" I
~
'"
~
1
~
1
<J
"
co
"
'"
Cl)
0
Cl)
'"
Cl)
en
a:1=
a:
'"
a:
i~
'"
u
a:
t
::;;
j
Now, a partial color change has been attained.
As in above, it enhances fast display change with less of
VRAM accessing by using various write modes.

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