Bit 3

This is the OSD override bit. This should be set to 0 for normal operation. When set to a 1, the video

outputs are disconnected and OSD only is displayed. This is useful for the OSD display of special

conditions such as “No Signal” and “Input Signal Out of Range”, to avoid seeing unsynchronized video.

Bit 4

Reserved and should be set to zero.

Bit 5

This is the Clamp Polarity bit. When set to a 0, the LM1237 expects a positive going clamp pulse.

When set to a 1, the expected pulse is negative going.

Bits 7–6

Reserved and should be set to zero.

Software Reset and Test Control Register

Register Name (address): SRTSTCTRL (0x843F)

7

654321

0

RSV

AID

RSV

RSV

RSV

RSV

RSV

SRST

Bit 0

When this bit is a 1, all registers except this one are loaded with their default values. All operations are

aborted, except data transfers in progress on the I

complete.

Bits 5–1

Reserved and should be set to zero.

Bit 6

This bit disables the register Auto-Increment feature of the I

Auto-Increment is disabled and when a 0, AI is enabled.

Bit 7

Reserved and should be set to zero.

Attribute Table and Enhanced Features

Each display character and SL in the Display Page RAM will have a 4-bit Attribute Table entry associated with it. The user should

note that two-color display characters and four-color display characters use two different Attribute Tables, effectively providing 16

attributes for two-color display characters and 16 attributes for four-color display characters.

For two-color characters the attribute contains the code for the 9-bit foreground color (Color 2), the code for the 9-bit background

color (Color 1), and the character’s enhanced features (Button Box, Blinking, Heavy Box, Shadowing, Bordering, etc.).

For four-color characters the attribute contains the code for the 9-bit Color 1, the code for the 9-bit Color 2, the code for the 9-bit

Color 3, the code for the 9-bit Color 4 and the character’s enhanced features (Button Box, Blinking, Heavy Box, Shadowing,

Bordering, etc.).

Two Color Attribute Format

Register Names (addresses):

value as described in Table 100.

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

RSV

RSV

RSV

RSV

RSV

RSV

RSV

RSV

RSV

RSV

EFB3

EFB2

EFB1

EFB0

C2B2

C2B1

15

14

13

12

11

10

987654321

0

C2B0

C2G2 C2G1 C2G0

C2R2

C2R1

C2R0

C1B2

C1B1

C1B0

C1G2 C1G1 C1G0

C1R2

C1R1

C1R0

Bits 8–0

These nine bits determine the background color (color1) which is displayed when the corresponding OSD

pixel is a 0.

Bits 17–9

These nine bits determine the foreground color (color2) which is displayed when the corresponding OSD pixel

isa1.

Bits 21 –18

These are the enhanced feature (EF) bits which determine which feature is applied to the displayed character.

The features and their corresponding codes are shown in Table 13.

Bits 31–22

Reserved and should be set to zero.

TABLE 13. Enhanced Feature Descriptions

Bits 21–18

Feature Description

0000b

Normal Display (color2/color1)

0001b

Blinking

0010b

Shadowing

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