23
1.10.
IC914 and IC915 on the Main Board are using the Character Generator IC MB90077PF104.
Description of this IC is as follows:
SCLK 2
STB 3
SIN 4
VMOD 5
Vcc 6
XDOUT 7
XD 8
20 N.C.
19 HSYNC
18 VSYNC
17 VBB
16 VBG
15 VBR
14 VOB
13 VOG
(TOP VIEW)
EXD 9
Vss 10
11 LHP
12 VOR
N.C. 1
Pin Name
I/O Description
1 N.C.
–
Non Connection
2 SCLK
I
Serial Clock Pulse input terminal.
3 STB
I
Strobe Pulse input terminal.
Serial Data should be read at rising
edge of this signal.
4 SIN
I
Serial Data Input terminal for
indication control.
5 VMOD
I
Effective edge changing input
terminal for Vertical Sync Signal.
"H" = Rising edge
"L"
= Falling edge
7 XDOUT
O XD Inverted signal output terminal.
8 XD
O XD signal output terminal.
9 EXD
I
External signal input terminal.
10 Vss
–
Ground terminal.
11 LHP
O
Line Hider Pulse output terminal.
12 VOR O
13 VOG
O
14 VOB
O
15 VBR
O
16 VBG
O
17 VBB
O
18 VSYNC
I
Vertical Sync signal input terminal.
19 HSYNC
I
Horizontal Sync signal input terminal.
20 N.C.
–
Non Connection
Color signal output terminals of
RGB system.
6 Vcc
–
Power supply terminal.
Blanking signal output terminals
which indicating output of the
character signal against the RGB
system.
Serial to
Parallel
Converter
8-bit
Latch
Instruction
Decoder
Bank
Control
Vertical Indication
Position Register
Horizontal Indication
Position Register
Write Row
Address
Write Column
Address
Column Address
Counter
Row Address
Counter
Indication Memory
VRAM (11-bit x 228)
VRAM Read Address
Indication Position
Detector
VRAM Access Control
Screen Indication CGROM
Access Control
Horizontal Position
Counter
Vertical Position
Counter
Character Size
Mask Pulse
Character, Back and
Frame Indication
Control Register
Blink
Period
Counter
Character Generator ROM
(12 x 18)-dot x 128-character
Sync Control Section
Dot Clock Generator
Dot Oscillation Control Register
VOB
VBB
VOG
VBG
VOR
VBR
LHP
SCLK
STB
SIN
Register
Control Bus
Data
Bus
CGROM
Raster Counter
VMOD
VSYNC
HSYNC
XDOUT
XD
EXD
VCC
V
SS
N.C.
N.C.
1
20
11
15
12
16
13
17
9
8
7
5
18
19
2
3
4
14
10
6
