STV0657 datasheet(83/105 Pages) STMICROELECTRONICS

83 / 105 page

CMOS Sensor; Customer Datasheet, Rev 3.0, 28 September 2000

VV5410 & VV6410

Commercial in confidence

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cd5410-6410f-3-0.fm

9.6.3

No data write followed by same location read.

When a location is to be read, but the value of the stored index is not known, a write message with no data byte must be written

first, specifying the index. The read message then completes the message sequence. To avoid relinquishing the serial to bus to

another master a repeated start condition is asserted between the write and read messages, i.e. no stop condition is asserted. In

this example, the

gain value (index = 3610) is read as 1510:

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

9.6.4

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. auto-load)

must be toggled.

The message sequence indexes

sf_setup register 108. If bit 0 is toggled high, low this will initiate a fresh auto-load. This is

achieved by writing two consecutive data bytes to the sensor. There is no requirement to re-send the register index before each

data byte.

9.6.5

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 below 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 40 : No data write followed by same location read.

3310

3610

3310

3610

1510 A

No data write

Read index and data

3210

2110

410

010

Write to

pin_mapping

Figure 41 : Same location multiple data write.

410

Toggle control bit

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