LM1253A National Semiconductor, LM1253A Datasheet - Page 29

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

CHARACTER ROM
0000h–2FFFh
3000h–3FFFh
4000h–7FFFh
DISPLAY PAGE RAM
8000h–81FF
LM1253A Address Map
Address
Address
Range
Range
R/W
R/W
R/W
R
R
ROM Character Fonts, 190 two-color Character Fonts that are read-only.
The format of the address is as follows:
A15–A14: Always zeros.
A13–A6: Character value (00h–BFh are valid values)
A5–A1: Row of the character (00h–11h are valid values)
A0: Low byte of line when a zero. High byte of line when a one.
The low byte will contain the first eight pixels of the line with data Bit 0 corresponding to the left
most bit in the Character Font line. The high byte will contain the last four pixels and data Bits
7–4 are “don’t cares”. Data Bit 3 of the high byte corresponds to the right most pixel in the
Character Font line.
ROM Character Fonts, 64 four-color Character Fonts that are read-only.
The format of the address is as follows:
A15–A14: Always zeros.
A13–A6: Character value (C0h–FFh are valid values)
A5–A1: Row of the character (00h–11h are valid values)
A0: Low byte of line when a zero. High byte of line when a one.
The low byte will contain the first eight pixels of the line with data Bit 0 corresponding to the left
most bit in the Character Font line. The high byte will contain the last four pixels and data Bits
7–4 are “don’t cares”. Data Bit 3 of the high byte corresponds to the right most pixel in the
Character Font line.
NOTE: The value of Bit 0 of the Character Font Access Control Register (I
zero, it indicates that the Bit 0 data value of the four-color pixels is being accessed via these
addresses. When the value of Bit 0 of the Access Control Register is a one, it indicates that the
Bit 1 data value of the four-color pixel is being accessed via these addresses.
RESERVED.
Display Page RAM Characters. A total of 512 display characters, skipped line, end-of-row and
end-of-window character codes may be supported via this range.
To support skipped lines and character attributes a number of special case rules are used when
writing to this range. (Refer to the Display Page RAM section of this document for more details.)
TABLE 4. Display Page RAM Address Map
TABLE 3. Character ROM Address Map
29
Description
Description
2
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