Panasonic BT-M1950Y Service Manual page 99

2. On-screen IC
The on-screen IC uses a Fujitsu MB90077PF for controlling the character display position on the monitor CRT.
• Maximum character quantity: 24 characters x 12 lines (288 characters)
• Character types: 128 characters, character code OOH - 7FH stored in internal character generator ROM
• Character composition: 12 x 18 dots per character
• Colors: 8 (character units), with edging, blink and back color functions using control ports (VOG, VOR, VOB,
VBG, VBR and VBB)
• Display synchronized to H and V sync; characters can be displayed regardless of signal system.
The IC102 MPU and interface connection is with three lines: clock (SCLK), data (SIN) and strobe (STB). Data are
transferred at 1 byte per 8 clock cycles and checked by the strobe pulse.
An LC oscillator circuit is connected to pins 8 and 9. Since the dot clock is produced with reference to -V SYNC and -H
SYNC (active Low) at pins 18 and 19, use is enabled regardless of the signal system.
The display outputs are TTL level R, G and B signals (VOG, VOR and VOB), enable signals (superimposed on source
signals) VBG, VBR and VBB applied to the IC108 OR circuit, and OSD ENABLE signal sent to the signal PB ASS'Y.
2-1 Block diagram
2 SCLK -
3 ST8 -
4 SIN -
Serial/parallel
5 VMODE ~
18-VSYNC
~
19
-HSYNC
~
7 -XDOUT ~
8 XD ~
9 EXD -
6 VCC
~
10
vss
~
converter
Sync
'®>
control
I
%>
Dot clock
oscillator
t
%>
Dot
-
oscillator 1--E- . _.
control
reg,,,,.,r
<l>
8 bit
<l>
Command
<l>
Bank
<l>
----
-
:----
latch decoder control
/~
t
- Resister control
- -
-
Data bus
t
q>
t
«>
t
<g>
V display H display Write line Line
position register position register address
~
address
------- --------
t <§>
Write line
-
Line
-
VRAM read address display
h1i''=
address
~
position detect
COU111t:1
«>
<§>
~
Qisplay memory
VRAM
VRAM
V position H position
access
counter counter
11bitx288
control
---~-~-
I
CGROM
/~
raster
~
counter
t
'
~
½,,-
~ VOB 14
~ VBB
17
Screen display
~ VOG
13
-
CGROM access
~ VBG
16
Character size
'
control
~ VOR
12
-
mask pulse 2
~
bits
x
1 2 lines
~ VBR
15
~ LHP 11
Character,
back, edging
·~
display control
t t
register
~
Character
<J)
generator ROM
(12
x
18) dots
x
·~
Blink period 128 characters
counter
Signals
<i> -
~
are grouped according lo function. Numbers correspond to the Block Diagram Description.
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