LM1253A National Semiconductor, LM1253A Datasheet - Page 34

• Manufacturer Part Number: LM1253A
• Description: Monolithic Triple 180 MHz I2C CRT Pre-amp With Integrated Analog On Screen Display (OSD) Generator
• Manufacturer: National Semiconductor

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Display Page RAM
The skip-line parameters associated with the next row must always be written to the location immediately after the preceding
row’s row-end character. The only exception to this rule is when a window-end character (value 00h) is encountered. It is impor-
tant to note that a row-end character should not precede a window-end character (otherwise the window-end character will be in-
terpreted as the next row’s skip-line parameters). Instead, the window-end character will both end the row and the window making
it unnecessary to precede it with a row-end character.
The I
tribute code to be sent in a string as follows:
Byte # 1 — I
Byte # 2 — LSB Address
Byte # 3 — MSB Address
Byte # 4 — Attribute Table Entry to use for the following characters
Byte # 5 — First display character, SL parameter, RE or WE control code.
Byte # 6 — Second display character, SL parameter, RE or WE control code.
Byte # 7 — Third display character, SL parameter, RE or WE control code.
.
.
Byte # n — Last display character in this color sequence, SL parameter, RE or WE control code to use the associated Attribute
Table Entry.
The Attribute Table Entry (Byte #4, of the above) is automatically associated with each subsequent display character or SL code
written. The following are examples of how the Display Page RAM associates to the actual On-Screen Display Window #1.
EXAMPLE #1:
A 3 X 3 character matrix of white characters on a black background is to be displayed using 2-color character codes:
The actual On-Screen Display of Window #1 is shown in Figure 41 . Note the dotted white lines are not shown on the monitor.
They are shown here to show where the character ends.
Notes:
• Every row must begin with an attribute and a SL. Display
• Every row except the last row of a Display Window must
• The last row in a Display Window must be a WE charac-
• The entire Display Window may be written in a single I
• The Attribute Table Entry that is associated with RE and
Page RAM memory location 8000h will always be associ-
ated with the SL of row 0 of Display Window #1.
end with an RE character. The character immediately af-
ter an RE character is always the SL value for the next
row.
ter. The WE character must NOT be preceded by an RE
character.
write sequence because the Attribute Table entry (i.e., the
color palette) does not change for the entire Display Win-
dow.
WE characters are “don’t cares”. In general it is most ef-
ficient just to allow them to be the same value as the At-
tribute Table Entry associated with the previous display
character.
2
C Format for writing a sequence of display characters is minimized by allowing sequential characters with the same at-
2
C Slave Address
(Continued)
FIGURE 41. Example 1 OSD
2
C
34
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• The colors of the characters and background can be
• The data shown in Table 9 is sent to the LM1253A in one
stored in a single location in the 2-color attribute table, in
location ATT0.
I
2
C transmission.