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TDA4887PS

160 MHz bus-controlled monitor video preamplifier

Philips Electronics 

Philips Semiconductors

160 MHz bus-controlled monitor video

preamplifier

Product specification

TDA4887PS

7.9 I2C-bus control

The TDA4887PS contains an I2C-bus receiver for several

control functions:

• Contrast register with control bits BRI, FPOL, DISV and

DISO

• Brightness control with 8-bit DAC

• Contrast control with 8-bit DAC

• OSD contrast control with 4-bit DAC

• Gain control for each channel with 8-bit DAC

• Internal feedback reference and external reference

voltage control for each channel with 8-bit DAC

• Black level for AC coupling with 3-bit DAC

• Depth of pedestal blanking with 2-bit DAC.

After power-up and after internal power-on reset of the

I2C-bus, the registers are set to the following values (for

most applications these settings guarantee a black screen

after power-up):

• Control bit FPOL set to logic 1

• Control bits BRI, DISV and DISO set to logic 0

• All other alignment registers set to logic 0 (minimum

value for control registers).

After an intermediate power dip, all registers are set to

their initial values and an internal Power-on reset bit will be

set with the consequence that the device will give no

acknowledge on the data byte after being first addressed.

The Power-on reset bit will be reset if the control register

is addressed. It is recommended to then refresh all

registers by using the auto-increment function.

7.10 I2C-bus data buffer

7.10.1 BUFFERED MODE

Adjustments via the I2C-bus are synchronized with vertical

blanking pulse at CLI:

• Most significant bit (MSB) of subaddress is set to logic 1

• Only one I2C-bus transmission in buffered mode is

accepted before the start of the vertical blanking pulse;

following transmissions receive no acknowledge

• Received data is stored in one internal 8-bit buffer

• Adjustments will take effect with detection of the first

vertical blanking pulse after the end of the

acknowledged I2C-bus transmission

• Waiting for vertical blanking pulse in buffered mode can

be interrupted by Power-on reset

• Auto-increment is not possible

• Buffered mode should be used for user adjustments

such as contrast, OSD contrast and brightness when a

picture is visible on the monitor.

7.10.2 DIRECT MODE

Adjustments via the I2C-bus take effect immediately:

• Most significant bit (MSB) of subaddress is set to logic 0

• Number of I2C-bus transmissions in direct mode is

unlimited

• Adjustments take effect directly at the end of each

I2C-bus transmission

• Direct mode can be used for all adjustments but large

changes of control values may appear as visual

disturbances in the picture on the monitor

• Auto-increment is possible

• Vertical blanking pulse is not necessary.

2001 Oct 19

11

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