LM1237_04 datasheet(33/42 Pages) NSC

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Control Register Definitions (Continued)

Character Height Register

20023439

Bits 7–0

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 324 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).

Enhanced Feature Register 1

Button Box Highlight Color

20023440

Bits 8–0

These determine the button box highlight color.

Bits 15–9

Reserved. These bits should be set to zero.

Enhanced Feature Register 2

Button Box Lowlight Color

20023441

Bits 8–0

These determine the button box lowlight color.

Bits 15–9

Reserved. These bits should be set to zero.

Enhanced Feature Register 3

Heavy Button Box Lowlight/Shading/Shadow

20023442

Bits 8–0

These registers determine the heavy button box lowlight, shading or shadow color.

Bits 15–9

Reserved. These bits should be set to zero.

ROM Signature Control Register

20023443

Bit 0

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.

Bits 7–1

Reserved. These should be set to zero.

ROM Signature Data Register

LM1237 Datasheet(PDF) 33 Page - National Semiconductor (TI)