STE2002 datasheet(20/51 Pages) STMICROELECTRONICS

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STE2002

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Bus Interfaces

To provide the widest flexibility and ease of use the STE2002 features three different methods for interfacing

the host Controller. To select the desired interface the SEL1 and SEL2 pads need to be connected to a logic

LOW (connect to GND) or a logic HIGH (connect to VDD). All the I/O pins of the unused interfaces must be

connected to GND.

All interfaces are working while the STE2002 is in Power Down

I2C Interface

The I2C interface is a fully complying I2C bus specification, selectable to work in both Fast (400kHz Clock) and

High Speed Mode (3.4MHz).

This bus is intended for communication between different Ics. It consists of two lines: one bi-directional for data

signals (SDA) and one for clock signals (SCL). Both the SDA and SCL lines must be connected to a positive

supply voltage via an active or passive pull-up.

The following protocol has been defined:

- Data transfer may be initiated only when the bus is not busy.

- During data transfer, the data line must remain stable whenever the clock line is high. Changes in the data line

while the clock line is high will be interpreted as control signals.

Accordingly, the following bus conditions have been defined:

BUS not busy: Both data and clock lines remain High.

Start Data Transfer: A change in the state of the data line, from High to Low, while the clock is High, define the

START condition.

Stop Data Transfer: A Change in the state of the data line, from low to High, while the clock signal is High,

defines the STOP condition.

Data Valid: The state of the data line represents valid data when after a start condition, the data line is stable

for the duration of the High period of the clock signal. The data on the line may be changed during the Low period

of the clock signal. There is one clock pulse per bit of data.

Each data transfer is initiated with a start condition and terminated with a stop condition. The number of data

bytes transferred between the start and the stop conditions is not limited. The information is transmitted byte-

wide and each receiver acknowledges with the ninth bit.

By definition, a device that gives out a message is called "transmitter", the receiving device that gets the signals

is called "receiver". The device that controls the message is called "master". The devices that are controlled by

the master are called "slaves"

Acknowledge. Each byte of eight bits is followed by one acknowledge bit. This acknowledge bit is a low level

put on the bus by the receiver, whereas the master generates an extra acknowledge related clock pulse.

A slave receiver which is addressed must generate an acknowledge after the reception of each byte. Also, a

master receiver must generate an acknowledge after the reception of each byte that has been clocked out of

the slave transmitter. The device that acknowledges has to pull down the SDA_IN line during the acknowledge

clock pulse. Of course, setup and hold time must be taken into account. A master receiver must signal an end-

of-data to the slave transmitter by not generating an acknowledge on the last byte that has been clocked out of

the slave. In this case, the transmitter must leave the data line High to enable the master to generate the STOP

SEL2

SEL1

Interface

Note

I2C

Read and Write; Fast and

High Speed Mode

Serial

Read and Write

Parallel

Read and Write

Not Used

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