STV-366-R01 STMICROELECTRONICS [STMicroelectronics], STV-366-R01 Datasheet - Page 18

• Manufacturer Part Number: STV-366-R01
• Description: 1.8V optical mouse sensor
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Serial control bus
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Serial control bus
General description
The 2-wire I2C serial interface bus is used to read and write the VT5366 registers.
The main features of the serial interface include:
Serial communication protocol
The co-processor must perform the role of communication ‘master’ and the sensor acts as a
‘slave’. The communication from host to sensor takes the form of 8-bit data with a maximum
serial clock frequency of 400 kHz. Since the serial clock is generated by the bus master it
determines the data transfer rate. Data transfer protocol on the bus is illustrated in
Figure 7.
Data format
Information is packed in 8-bit packets (bytes) always followed by an acknowledge bit. The
internal data is produced by sampling sda at a rising edge of scl . The external data must be
stable during the high period of scl . Exceptions to this are start (S) or stop (P) conditions
when sda falls or rises respectively, while scl is high.
A message contains at least two bytes. Its begins with a start condition and ends with either
a stop condition or another start condition In this situation the (second) start is referred to as
a repeated start and is shown as (Sr). The first byte of a transaction always contains the
device address byte in the upper 7 bits with the LSB indicating the data direction; 1 for read
or 0 write . Thus the 8 bit device address for the VT5366 is 0x20 for writing and 0x21 for
reading.
Figure 8.
SDA
SCL
–
–
–
–
–
Start condition
Variable length read/write messages
Indexed addressing of information source or destination within the sensor
Automatic update of the index after a read or write message
Message abort with negative acknowledge from the master
Byte oriented messages
S
Serial Interface data transfer protocol
VT5366 serial interface address
MSB
0
1
0
2
Address or data byte
1
3
0
4
0
5
0
6
0
7
LSB
R/W
8
Acknowledge
A
Stop condition
Figure 7
P
VT5366
.