STCF04 datasheet(19/43 Pages) STMICROELECTRONICS

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STCF04

Detailed description

Doc ID 022927 Rev 3

19/43

8.1.10

Byte format

Every byte transferred to the SDA line must contain 8 bits. Each byte must be followed by an

acknowledge bit. The MSB is transferred first. One data bit is transferred during each clock

pulse. The data on the SDA line must remain stable during the HIGH period of the clock

pulse. Any change in the SDA line at this time is interpreted as a control signal.

Figure 7.

Bit transfer

8.1.11

Acknowledge

The master (microprocessor) puts a resistive HIGH level on the SDA line during the

acknowledge clock pulse (see

Figure 8). The peripheral (STCF04) that acknowledges must

pull down (LOW) the SDA line during the acknowledge clock pulse, so that the SDA line is

stable LOW during this clock pulse. The peripheral which has been addressed must

generate an acknowledge pulse after the reception of each byte, otherwise the SDA line

remains at the HIGH level during the ninth clock pulse duration. In this case, the master

transmitter can generate the STOP information in order to abort the transfer. The STCF04

does not generate the acknowledge bit if the VI supply is below 2.7 V.

Figure 8.

Acknowledge on I²C bus

8.1.12

Interface protocol

The interface protocol is composed of (

Table 8):

- A START condition (START)

- A device address + R/W bit (read =1 / write =0)

- A register address byte

AM11867v1

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