TABLE 8. LM1237 Two-Color Attribute Registers (Continued)

Register

Address

D7

D6

D5

D4

D3

D2

D1

D0

ATT2C1n

+1

C2B[0]

C2G[2:0]

C2R[2:0]

C1B[2]

ATT2C2n

+2

X

X

EF[3:0]

C2B[2:1]

ATT2C3n

+3

XXXX

XXX

X

Note: Set reserved bits to 0.

The attributes for two-color display characters may be written or read via the following address format:

A15–A6: Always a binary 1000010001.

A5–A2: Attribute code n (0x0–0xF are valid values).

A1–A0: Determines which of the 3 bytes is to be accessed.

Note: In the table, n indicates the attribute number 0

≤ n ≤ 15.

Note: When writing, bytes 0 through 2 must be written in order. Bytes 0 through 2 will take effect after byte 2 is written. Since byte 3 contains all reserved bits, this

byte may be written, but will have no effect.

When reading, it is OK to read only one, two, or all three bytes.

If writing more than one 2-color attributes using the auto increment feature, all four bytes must be written.

Four-Color Attribute Table

TABLE 9. LM1237 Four-Color Attribute Registers

Register

Address

D7

D6

D5

D4

D3

D2

D1

D0

ATT4C0n

8500 +

(n*8)

C1B[1:0]

C1G[2:0]

C1R[2:0]

ATT4C1n

+1

C2B[0]

C2G[2:0]

C2R[2:0]

C1B[2]

ATT4C2n

+2

X

X

EF[3:0]

C2B[2:1]

ATT4C3n

+3

XXXX

XXX

X

ATT4C4n

+4

C3B[1:0]

C3G[2:0]

C3R[2:0]

ATT4C5n

+5

C4B[0]

C4G[2:0]

C4R[2:0]

C3B[2]

ATT4C6n

+6

XXXX

XX

C4B[2:1]

ATT4C7n

+7

XXXX

XXX

X

Note: Set reserved bits to 0.

The attributes for four-color display characters may be written or read via the following address format:

A15–A7: Always a binary 100001010.

A6–A3: Attribute code n (0x0–0xF are valid values).

A2–A0: Determine which of the six bytes of the attribute is to be accessed.

Note: In the table, n indicates the attribute number 0

≤ n ≤ 15.

Note: When writing, bytes 0 through 2 must be written in order and bytes 4 to 6 must be written in order. Bytes 0 through 2 will take effect after byte 2 is written.

Bytes 4 through 6 will take effect after byte 6 is written. Since bytes 5 and 7 contain all reserved bits, these bytes may be written, but no effect will result.

When reading, it is OK to read only one, two, or all three bytes.

If writing more than one 4-color attributes using the auto increment feature, all eight bytes must be written.

Display Page RAM

THE OSD WINDOW

The Display Page RAM contains all of the 8-bit display

character codes and their associated 4-bit attribute codes,

and the special 12-bit page control codes — the row-end,

skip-line parameters and window-end characters.

The LM1237 has a distinct advantage over many OSD gen-

erators that it allows variable size and format windows. The

window size is not dictated by a fixed geometry area of RAM.

Instead, 512 locations of 12-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.

CHARACTER CODE AND ATTRIBUTE CODE

Each of the 512 locations in the page RAM is comprised of a 12-bit code consisting of an 8-bit character or control code, and a

4-bit attribute code:

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