VV6404 datasheet(39/54 Pages) STMICROELECTRONICS

39 / 54 page

VV5404 & VV6404

CD5404-6404F-A

39/54

As mentioned in the previous example, the read message is terminated with a negative acknowledge (A) from the

master.

5.6.4

Same location multiple data write.

It may be desirable to write a succession of data to a common location. This is useful when the status of a bit,(e.g.

requesting a new black calibration), must be toggled.

The message sequence indexes setup1 register. If bit 1 is toggled low, high low this will initiate a fresh black

calibration. This is achieved by writing three consecutive data bytes to the sensor. There is no requirement to re-send

the register index before each data byte.

5.6.5

Same location multiple data read

When an exposure related value (fineH, fineL, coarseH, coarse L, gain or clk_div) is written, it takes effect on the

output at the beginning of the next video frame, (remember that the application of the gain value is a frame later than

the other exposure parameters). To signal the consumption of the written value, a flag is set when any of the exposure

or gain registers are written and is reset at the start of the next frame. This flag appears in status0 register and may

be monitored by the bus master. To speed up reading from this location, the sensor will repeatedly transmit the current

value of the register, as long as the master acknowledges each byte read.

In the next example, a fineH exposure value of 0 is written, the status register is addressed (no data byte) and then

constantly read until the master terminates the read message.

Figure 21 : No data write followed by same location read.

3210

3610

3310

3610

1510 A

No data write

Read index and data

010

3210

1710

210

010

Write setup1

Turn off ABC

Toggle “Force Black Cal.”.

Figure 22 : Same location multiple data write.

3210

3310

3210

010

3310

010

Write fineL with zero

Address the status0 reg.

Read continuously...

...until flag reset

Figure 23 : Same location multiple data read.

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