AL875

Preliminary version subject to change without notice

January 25, 2001

16

6.4 Automatic Positioning Control

The input horizontal and vertical starting and ending positions are detected to ensure that the whole

picture fits into the displayable region of the screen. Two modes of position detection are provided: 1-

line detection and whole-frame detection.

The 1-line detection can be performed by choosing any

horizontal line (reg.#10h) or vertical line (reg.#19h), to check in what range the luma data is larger

than the threshold value defined by DATA_TH (reg.#11h). When the threshold for the vertical line is

different from the horizontal line, an additional register VDATA_TH (reg.#0Fh) can be used for

vertical threshold and it is enabled by reg.#06h<7>. Any luma data lower than the threshold value is

considered blanking period. The following drawing shows the related registers:

DELAY

CKREF

CLOCK

BUFFER

CKAO

PHASE B (#0Ch<3:0>)

CKBO

4

/N

COUNTER

HSFB

DIVIDER

#0Ah<3:0> & #0Bh<7:0>

12

Input/Output pin

AL875-07b Clock Distribution Circuitry

Inverter

INV

CKADCO

ADC sampling clock

Internal logic clock