VV6404 datasheet(43/54 Pages) STMICROELECTRONICS

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VV5404 & VV6404

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6.8

Synchronising 2 or More Cameras

A rising edge on the SIN pin re-synchronises the sensor’s internal video timing logic and clock generators to 5 pixels

before the end of the start of frame control sequence in line 0 (assuming the Setup2 register has been programmed

correctly with the value 30). By supplying an external timing signal to SIN, with a period equal to 2 frames (see Figure

28), 2 or more cameras can be synchronised together.

For proper synchronisation, the pixel counter register Setup2 must be written with 30, which will cause SIN to reset

the video timing to 5 pixel periods before the end of the start of frame control sequence. SIN is sampled internally by

the system clock, CKI. If all cameras are supplied with the same clock signal then the reset generated by SIN will

synchronise all the cameras to the same point in time. However, if the cameras being synchronised are running at

the same frequency but each camera has its own crystal, then there could be upto one system clock period of skew

between the cameras. This skew will vary over time due to the slight mis-matches between frequencies of the different

crystals.

CLKI

(MHz)

Clock Div Reg

Divisor

Pixel

Frequency

(MHz)

Frame rate (fps)

Comments

bit 1

bit 0

30 fps

25 fps

7.15909

3.57954

30.0

25.0

Default

7.15909

1.78977

15.0

12.5

7.15909

0.89489

7.50

6.25

7.15909

0.44744

3.75

3.125

Table 29 : Clock Divisors for an externally generated clock signal.

CLKI

(MHz)

Clock Div Reg

Divisor

Pixel

Frequency

(MHz)

Frame rate (fps)

Comments

bit 1

bit 0

30 fps

25 fps

14.31818

7.15909

Not Valid

14.31818

3.57954

30.0

25.0

14.31818

1.78977

15.0

12.5

14.31818

0.89489

7.50

6.25

Table 30 : Clock Divisors for a 14.31818 MHz Crystal

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