VS6724 Datasheet, PDF (46/118 Pages) STMicroelectronics – 2 Megapixel single-chip camera module

Host communication - I²C control interface
Figure 33. Random location, single write
16-bit Index, 8-bit Data, Random Location, Single Data Write
Previous Index Value, K
Index M
S DEV ADDR R/W A
DATA
A
DATA
A
‘0’ (Write)
INDEX[15:8]
INDEX[7:0]
Index[15:0]
value, M
DATA
A/A P
DATA[7:0]
DATA[7:0]
From Master to Slave
From Slave to Master
S = START condition
Sr = repeated START
P = STOP Condition
A = Acknowledge
A = Negative acknowledge
VS6724
3.3.2
Current location, single data read
For the master reading from the slave the R/W bit is set to one. The register index of the
data returned is that accessed by the previous read or write message.
The first data byte returned by a read message is the contents of the internal index value
and NOT the index value. This was the case in older V2W implementations.
Note that the read message is terminated with a negative acknowledge (A) from the master:
it is not guaranteed that the master will be able to issue a stop condition at any other time
during a read message. This is because if the data sent by the slave is all zeros, the SDA
line cannot rise, which is part of the stop condition.
Figure 34. Current location, single read
16-bit index, 8-bit data current location, single data read
Previous Index Value, K
S DEV ADDR R/W A
‘1’ (Read)
DATA
AP
DATA[7:0]
DATA[7:0]
From Master to Slave
From Slave to Master
S = START Condition
Sr = repeated START
P = STOP Condition
A = Acknowledge
A = Negative Acknowledge
3.3.3
Random location, single data 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.
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