LM1237_04 datasheet(34/42 Pages) NSC

34 / 42 page

Control Register Definitions (Continued)

987654321

CRC15 CRC14 CRC13 CRC12 CRC11 CRC10 CRC9 CRC8 CRC7 CRC6 CRC5 CRC4 CRC3 CRC2 CRC1 CRC0

Bits 15–0

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.

Display Window 1 Horizontal Start Location Register

321

1H7

1H6

1H5

1H4

1H3

1H2

1H1

1H0

Bits 7–0

There are two possible OSD windows which can be displayed simultaneously or individually. This register

determines the horizontal start position of Window 1 in OSD pixels (not video signal pixels). The actual

position, to the right of the horizontal flyback pulse, is determined by multiplying this register value by 4 and

adding 30. Due to pipeline delays, the first usable start location is approximately 42 OSD pixels following the

horizontal flyback time. For this reason, we recommend this register be programmed with a number larger

than 2, otherwise improper operation may result.

Display Window 1 Vertical Start Location Register

321

1V7

1V6

1V5

1V4

1V3

1V2

1V1

1V0

Bits 7–0

This register determines the Vertical start position of the Window 1 in constant-height character lines (not

video scan lines). The actual position is determined by multiplying this register value by 2. (Note: each

character line is treated as a single auto-height character pixel line, so multiple scan lines may actually be

displayed in order to maintain accurate position relative to the OSD character cell size. See the Constant

Character Height Mechanism section.) This register should be set so the entire OSD window is within the

active video.

LM1237 bảng dữ liệu(PDF) 34 Page - National Semiconductor (TI)