STV6886 datasheet(24/43 Pages) STMICROELECTRONICS

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STV6886

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In order to choose the right sync priority the MCU

may proceed as follows (see I2C Bus Address Ta-

ble):

– refresh the status register,

– wait at least for 20ms (Max. vertical period),

– read the status register.

Sync priority choice should be :

Of course, when the choice is made, we can re-

fresh the sync detections and verify that the ex-

tracted Vsync is present and that no sync type

change has occurred. The sync processor also

gives sync polarity information.

1.7 IC status

The IC can inform the MCU about the 1st horizon-

tal PLL and vertical section status (locked or not)

and about the XRAY protection (activated or

not).Resetting the XRAY internal latch can be

done either by decreasing the VCC supply or di-

rectly resetting it via the I2C interface.

1.8 Sync Inputs

Both H/HVIN and VSYNCIN inputs are TTL com-

patible triggers with hysteresis to avoid erratic de-

tection. Both inputs include a pull up resistor con-

nected to VDD.

1.9 Sync Processor Output

The sync processor indicates on bit D8 of the sta-

tus register whether 1st PLL is locked to an incom-

ing horizontal sync. Its level goes to low when

locked. This information is also available on pin 3 if

sub-address 02 D8 is equal to 1. When PLL1 is un-

locked, pin 3 output voltage becomes higher than

6V. When it is locked, the HMoiré waveform is

available on pin 3 (max voltage: 3V).

2 HORIZONTAL PART

2.1 Internal Input Conditions

A digital signal (horizontal sync pulse or TTL com-

posite) is sent by the sync processor to the hori-

zontal input. It may be positive or negative (see

Figure 5).

Using internal integration, both signals are recog-

nized if Z/T < 25%. Synchronization takes place on

the leading edge of the internal sync signal.

The minimum value of Z is 0.7

µs.

Another integration is able to extract the vertical

pulse from composite sync if the duty cycle is high-

er than 25% (typically d = 35%),

(see Figure 6).

Figure 5.

Figure 6.

The last feature performed is the removal of these

equalization pulses which fall in the middle of a

line, to avoid parasitic pulses on the phase compa-

rator (which would be disturbed by missing or ex-

traneous pulses). This last feature is switched on/

off by sub-address 0F D8. By default [0], equaliza-

tion pulses will not be removed.

Vextd

H/V

det

Sync

priority

Subaddress

03 (D8)

Comment

Sync type

Yes

Separated H&V

Yes

Composite TTL

H&V

CSync

Integ.

VSyn

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