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VIDEO OUTPUT WAVEFORMS
Reg.
Description
#
RO
HORIZONTAL TOTAL
RI
HORIZONTAL DISPLAYED
R2
HORIZONTAL SYNC POSITION
R3
HORIZONTAL SYNC WIDTH
R4
VERTICAL TOTAL
R5
VERTICAL TOTAL ADJUST
R6
VERTICAL PISPLAYED
R7
VERTICAL SYNC POSITION
R8
INTERLACE MODE
R9
MAX. SCAN LINE ADDRESS
RIO
CURSOR START
RII
CURSOR END
RI2
START ADDRESS IH)
RI3
START ADDRESS III
RI4
CURSOR ADDRESS IH)
RI5
CURSOR ADDRESS I L)
RI6
LIGHT PEN ADDR. IH)
RI7
LIGHT PEN ADDR. IL)
-: Not used the function.
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c9
' - - - - - '
-
P C-720D
Figure
2~34.
Block diagram of display circuit
2-2-17-1. Internal Registers of the MN12BB
(Table 2-21)
There are nineteen registers in the MN1288. They are used to define
parameters for the CRT monitor. The Index register which is one
of those registers, is used for a pointer to the other 18 registers. It
is assigned by the CPU at the 110 address 3B4H for the monochrome
board or 3D4H for the color board.
The Index register must be first loaded with the necessary register
number, and then the Data register is loaded with the information
to be placed in the selected register.
The Data register is assigned by the CPU at the 110 address 3B5H
for the monchrome board or 3D5H for the color board.
The following table shows the value that must be loaded into the
MN1288 internal registers, and Figure
2~35
shows the each value
on the CRT monitor.
Table
2~21.
Register definition
2-23
Read/
Write
W
W
W
W
W
W
W
W
W
W
W
W
W
W
R/W
R/W
R
R
( NV 01
VERTICAL
DISPLAYED
CHARl\CTERS
MONO.
Color
board
40
x
25
80 x 25
GRPH
Item
Unit
61
38
71
38
Nht
Characters
50
28
50
28
Nht
Characters
52
20
5A
20
Nhsp
Characters
OF
OA
OA
OA
Nhsw
Characters
19
IF
IF
7F
Nvt
Characters Row
06
06
06
06
Nadj
Scan Line
19
19
19
64
Nvd
Characters Row
19
IC
IC
70
NV5P
Characters Row
02
02
02
02
-
00
07
07
01
Nr
Scan Line
DB
06
06
06
Nr
Scan Line
DC
07
07
07
Nr
Scan Line
-
00
00
00
-
-
00
00
00
-
XX
xx
XX
XX
-
XX
XX
XX
XX
-
-
XX
XX
XX
-
-
XX
XX
XX
-
HORIZONTAL TOTAL CHARACTERS
~~~~'
..
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(1'1, +
11
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I-+--+--+-----------f----j
~~RESS
HORIZONTAL OISPLAYED CKI\RIICTERS
Figure
2~35.
Register description
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