LM1247 National Semiconductor, LM1247 Datasheet - Page 34

• Manufacturer Part Number: LM1247
• 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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Control Register Definitions
Character Height Register:
ROM Signature Control Register:
ROM Signature Data:
Bits 6–0
Bit 7
Bits 7–0
Enhanced Feature Register 1:
Enhanced Feature Register 2:
Enhanced Feature Register 3:
X
X
X
Bits 8–0
Bits 15–9
Bits 8–0
Bits 15–9
Bits 8–0
Bits 15–9
Bit 0
Bits 7–1
Bits 15–0
X
X
X
This register determines the duration of the vertical blanking signal in scan lines. When vertical blanking is
enabled, it is recommended that this register be set to a number greater than 0x0A.
Reserved. This bit should be set to zero.
This register determines the OSD character height as described in the section Constant Character Height
Mechanism. The values of this register is equal to the approximate number of OSD height compensated lines
required on the screen, divided by 4. This value is not exact due to the approximation used in scaling the
character.
Example: If approximately 384 OSD lines are required on the screen (regardless of the number of scan lines)
then the Character Height Control Register is programmed with 81 (0x51).
CHSDWCTRLB1 (0x840A)
ROMSIGDATAB1 (0x840F)
These determine the button box highlight color.
Reserved. These bits should be set to zero.
These determine the button box lowlight color.
Reserved. These bits should be set to zero.
These registers determine the heavy button box lowlight, shading or shadow color.
Reserved. These bits should be set to zero.
This controls the calculation of the ROM signature. Setting this bit causes the ROM to be read
sequentially and a 16-bit checksum calculated over the 256 characters. The sum, modulo 65535,
is stored in the ROM Signature Data Register, and this bit is then automatically cleared.
Reserved. These should be set to zero.
This is the checksum of the 256 ROM characters truncated to 16 bits (modulo 65535). All devices
with the same masked ROM will have the same checksum.
BBHLCTRLB1 (0x8406)
X
X
X
BBLLCTRLB1 (0x8408)
Reserved
Reserved
Reserved
X
X
X
X
X
X
X
X
X
X
X
X
(Continued)
CHARHTCTRL (0x8404)
ROMSIGCTRL (0x840D)
X
X
X
Reserved
16 Bit Checksum
X
Highlight - Green
CRC[15:0]
Lowlight - Green
Shadow - Green
CH[7:0]
34
G[2:0]
G[2:0]
G[2:0]
X
X
Heavy Button Box Lowlight/Shading/Shadow
ROMSIGDATAB0 (0x840E)
CHSDWCTRLB0 (0x8409)
BBHLCTRLB0 (0x8405)
BBLLCTRLB0 (0x8407)
Highlight - Red
Lowlight - Red
Shadow - Red
X
R[2:0]
R[2:0]
R[2:0]
check
CRS
Button Box Highlight Color
Button Box Lowlight Color
Highlight - Blue
Lowlight - Blue
Shadow - Blue
B[2:0]
B[2:0]
B[2:0]