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参数资料
| 型号： | MC144144P |
| 厂商： | MOTOROLA INC |
| 元件分类： | 颜色信号转换 |
| 英文描述： | Digital Signal Processors 44-JLCC -55 to 125 |
| 中文描述： | COLOR SIGNAL DECODER, PDIP18 |
| 封装： | PLASTIC, DIP-18 |
| 文件页数： | 14/44页 |
| 文件大小： | 565K |
| 代理商： | MC144144P |
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MC144144
14
MOTOROLA
This approach was used because shrinking the capitals to
make room for the accent mark within the character cell
makes poor quality characters and in some cases there
would be no differentiation between the capital and lower
case letter. It also has the advantage of minimizing the ROM
size and providing a good readable font that closely matches
what is normally seen in print.
In the unlikely case of a conflict between an accented capi-
tal letter in one row and a lowercase descender in the same
character position in the row above, the descender is given
priority. It is believed that the improved readability of our ap-
proach over shrunk capital letters far outweighs this potential
conflict and results in a cost effective compromise for provid-
ing a full, extended features implementation.
The extended characters share their address space with
the ODS graphics characters. When a BOX display is used
the extended character set is in force. However, if a drop
shadow display is used the graphics characters are in force.
For caption and text display modes, if drop shadow is set, the
user must also command the MC144144 to switch back to
extended characters.
Text Mode Display
When TEXT mode is selected normally, a black box will be
displayed as long as valid Line 21 code in the field selected is
being detected. The MC144144 provides the option to make
the box blue instead of black. This option will hold for cap-
tions as well as text.
The default TEXT display mode uses a 15 row by 34 char-
acter black box. TEXT characters will be displayed as they
are received starting in the top row. Successive carriage re-
turns will move the display down successive rows until all 15
rows have been displayed. Thereafter, the text will scroll up
as new characters are added to the bottom row.
If the data for the selected channel is interrupted by a com-
mand for another channel, data processing stops but the dis-
play will remain. When a resume text command is received,
data processing will resume and the new characters will be
added starting at the position that the display row/column
pointer was in at the interruption of data processing. If a start
text command is received, the display will be cleared and
new characters will be displayed starting in row 1, column 1
(left side).
The number of display rows and the location (base row) of
the TEXT box can be altered by the user. In this way, the user
can decide how much of the screen can be covered when
displaying non–program related information.
When scrolling, the display will shift one scan line per
frame until a complete row has been scrolled. If a carriage
return is received before scrolling is complete, the display will
immediately complete the “scroll” by jumping up the remain-
ing scan lines and starts displaying the new text.
Caption Mode Display
According to the FCC specifications, caption data can ap-
pear in any of the 15 display rows but a single caption may
consist of no more than four rows. The form of the caption
display depends on the caption mode indicated by the trans-
mitted caption command, pop–on, paint–on, or roll–up. The
MC144144 can display a single caption having as many as
eight rows. When any of the CAPTION display modes have
been selected, the screen will be transparent (display box is
only present when a caption is being displayed).
Pop–on captions work with two caption memories. One of
them is normally displayed while the other is being used to
accumulate new caption data. A new caption is popped–on
by swapping the two memories with the end of caption (EOC)
command. When the on–screen memory is erased, the
screen is blank (transparent) and the memory will default to
the row/column pointer at row 1, column 1 and monochrome
non–underlined.
When caption mode is selected, the decoder will process
any data following the resume caption loading (RCL) com-
mand (or the EOC). Normally, this command will be followed
by a preamble address code (PAC) to indicate the row, col-
umn, and character attributes to be used with the following
data. If no PAC is received the data will be added to the loca-
tion last indicated by the row/column pointer prior to the re-
ceipt of the RCL command.
Paint–on caption mode is essentially equivalent to the
pop–on mode except that the data received after the resume
direct captioning (RDC) command is written to the on–screen
memory rather than the off–screen memory. All the rules for
PACs, midcodes, etc., are otherwise the same.
Roll–up caption mode presents a “text” like display that is
limited to two, three, or four rows, depending on the resume
roll–up (RUn) command used. The PAC following the RUn
command is used as the BASE ROW for the ROLL–UP dis-
play. The BASE ROW will be the “bottom” row of the ROLL–
UP display. In this case black box does not appear until
characters are being displayed and box is only wide enough
to provide a leading and trailing box in each line. The new
data appears in the bottom row and as each carriage return
is received, the row scrolls up and the new data added to the
bottom. When the number of rows indicated by the resume
command has been reached, the data in the top row scrolls
off as new data is added to the bottom.
The TAB (INDENT) PAC permits placing captions starting
at four character boundaries in any caption row. The TAB
OFFSET command provides the means for adjusting the
starting position for a caption at any column position in the
current row.
XDS Mode Display
Two XDS display modes are provided. One provides in-
formation about the current program that would be of interest
for “channel grazing”. The second display shows the grazing
packets plus additional XDS packets which will inform the
viewer about the program content. Information will be dis-
played as it is received. The display uses the drop shadow
mode with 15 scan lines per row.
The XDSG mode is the GRAZE (channel grazing) display.
The display contains three rows of information at the top of
the screen, formatted for easy reading. They will contain the
following XDS packet information:
Row 1, Grn –
Network Name – Call Letters
Row 2, Ital, Und –
Program Name (title)
Row 3, Cyan –
Program Length – Time In Show
The XDSF mode is the FULL (information) display. This
display shows the same information as the GRAZE display
and adds the program type as well the first four program de-
scription rows (if transmitted). Although XDS defines eight
program description rows, the first four are identified as con-
taining the most important information and are the ones most
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