LM1276AAA National Semiconductor, LM1276AAA Datasheet - Page 30

• Manufacturer Part Number: LM1276AAA
• Description: 150 MHz I2C Compatible RGB Preamplifier with Internal 512 Character OSD ROM, 512 Character RAM and 4 DACs
• Manufacturer: National Semiconductor

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Register
V_BP0
V_BP1
V_FP0_PRV
V_FP1_PRV
V_SYN_PRV
V_BP0_PRV
V_BP1_PRV
HB CONTROL
STATUS
MCU COMMAND
SUB COMMAND
SEQ NUM
PLL LOCK
H INPUT SEL
LM1276 Address Map
Building Display Pages
THE OSD WINDOW
The Display Page RAM contains all of the 9-bit display character codes and their associated 4-bit attribute codes, and the special
13-bit page control codes — the End-of-Line, skip-line parameters and End-of-Screen characters. The LM1276 has a distinct
advantage over many OSD Generators in that it allows variable size and format windows. The window size is not dictated by a
fixed geometric area of RAM. Instead, 512 locations of 13-bit words are allocated in RAM for the definition of the windows, with
special control codes to define the window size and shape.
Window width can be any length supported by the number of pixels per line that is selected divided by the number of pixels in a
character line. It must be remembered that OSD characters displayed during the monitor blanking time will not be displayed on
the screen, so the practical limit to the number of horizontal characters on a line is reduced by the number of characters within
the horizontal blanking period.
The EOS code tells the OSD generator that the character codes following belong to another displayed window at the next window
location. An EOS code may follow normal characters or an SL code, but never an EOL control code, because EOL is always
followed by an AC plus an SL code.
WRITING TO THE PAGE RAM
The Display Page RAM can contain up to 512 of the above listed characters and control codes. Each character, or control code
will consume one of the possible 512 locations. For convenience, writing a 1 to bit 3 of the Frame Control Register (0x8400) resets
all page RAM values to zero. This should be done at power up to avoid unpredictable behavior.
Display Window 1 will also start at the first location (corresponding to the I
the Skip-Line (SL) code associated with the first line of Display Window 1. The attribute for this SL code must be written before
the SL code itself, and will be stored in the lower four bits of this memory location. Subsequent locations should contain the
characters to be displayed on line 1 of Display Window 1, until the EOL code or EOS code is written into the Display Page-RAM.
The skip-line parameters associated with the next line must always be written to the location immediately after the preceding line’s
End-of-Line character. The only exception to this rule is when an End-of-Screen character (value 0x0000) is encountered. It is
important to note that an End-of-Line character should not precede an End-of-Screen character (otherwise the End-of-Screen
character will be interpreted as the next line’s skip-line code). Instead, the End-of-Screen code will end the line and also end the
window, making it unnecessary to precede it with an EOL. The I
minimized by allowing sequential characters with the same attribute code to send in a string as follows:
Byte #1: I
Byte #2: LSB Register Address
Byte #3: MSB Register Address
Byte #4: Attribute Table Entry to use for the following s skip-line code or characters
Byte #5: First display character, SL parameter, EOL or EOS control code
Byte #6: Second display character, SL parameter, EOL or EOS control code
Byte #7: Third display character, SL parameter, EOL or EOS control code
Byte #n: Last display character in this color sequence, SL parameter, EOL or EOS control code to use the associated Attribute
Table Entry.
2
C Slave Address
Address
0xFFFD
0x858A
0x858B
0x858C
0x858D
0x858E
0x859A
0xFFF8
0x8589
0x858F
0x8590
0x8591
0x8592
0x8593
Default
0xFF
0xFF
0xFF
0xFF
0xFF
0xFF
0xFF
0x07
0x07
0x07
0x40
0x00
0x00
0x01
TABLE 13. LM1276 Auto Size Registers (Continued)
(Continued)
INTR_EN
INTR
RSV
RSV
D7
LIMIT
RSV
RSV
RSV
D6
30
WHLDIS
LOCK
RSV
RSV
RSV
SET
D5
2
C Format for writing a sequence of display characters is
2
MCU COMMAND[7:0]
C address 0x8000). This location must always contain
SUB COMMAND[7:0]
VSYNC PREV [7:0]
FSHEN
LOCK
VFP PREV [7:0]
VBP PREV [7:0]
ORR
RSV
RSV
SEQ NUM[7:0]
D4
VBP[7:0]
HSEL
RSV
RSV
RSV
D3
RSV
RSV
RSV
RSV
D2
VBP PREV[10:8]
VFP PREV[10:8]
VBP[10:8]
RSV
RSV
RSV
RSV
D1
RSV
RSV
RSV
RSV
D0