VDP3108B datasheet(22/72 Pages) MICRONAS

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PRELIMINARY DATA SHEET

VDP 31xxB

Micronas

In each field two sets of measurements can be taken:

a) The picture tube measurement returns results for

– cutoff R

– cutoff G

– cutoff B

– white drive R or G or B (sequentially)

b) The picture measurement returns data on

– active picture maximum current

– active picture minimum current

The tube measurement is automatically started when

the cutoff blue result register is read. Cutoff control for

RGB requires one field only while a complete white-drive

control requires three fields. If the measurement mode

is set to ‘offset check’, a measurement cycle is run with

the cutoff/whitedrive signals set to zero. This allows to

compensate the MADC offset as well as input the

leakage currents. During cutoff and whitedrive measure-

ments, the average beam current limiter function (ref.

2.9.3.) is switched off and a programmable value is used

for the brightness setting. The start line of the tube mea-

surement can be programmed via I2C-bus, the first line

used for the measurement, i.e. measurement of cutoff

red, is 2 lines after the programmed start line.

The picture measurement must be enabled by the con-

trol microprocessor after reading the min./max. result

registers. If a ‘1’ is written into bit 2 in subaddress 25, the

measurement runs for one field. For the next measure-

ment a ‘1’ has to be written again. The measurement is

always started at the beginning of active video.

The vertical timing for the picture measurement is pro-

grammable, and may even be a single line. Also the sig-

nal bandwidth is switchable for the picture measure-

ment.

Two horizontal windows are available for the picture

measurement. The large window is active for the entire

active line. Tube measurement is always carried out with

the small window. Measurement windows for picture

and tube measurement are shown in Figure 2–23.

active video

field 1/ 2

small window for tube

measurement (cutoff, white drive)

large window for active picture

picture meas. start

tube measurement

picture meas. end

Fig. 2–23: Windows for tube and picture measure-

ments

2.9.2. SCART Output Signal

The RGB output of the VDP 31xxB can also be used to

drive a SCART output. In the case of the SCART signal,

the parameter CLMPR (clamping reference) has to be

set to 1. Then, during blanking, the RGB outputs are au-

tomatically set to 50% of the maximum brightness. The

DC offset values can be adjusted with the cutoff parame-

ters CR, CG, and CB. The amplitudes can be adjusted

with the drive parameters WDR, WDG, and WDB.

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