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2015-07-0033

PT0523-4

8/18/15

10

PI4MSD5V9542A

2 Channel I2C bus Multiplexer

with Interrupt Logic

Both data and clock lines remain HIGH when the bus is not busy. A HIGH-to-LOW transition of the data line

while the clock is HIGH is defined as the START condition (S). A LOW-to-HIGH transition of the data line while the

clock is HIGH is defined as the STOP condition (P)

Figure 8. Definition of Start and Stop Conditions

A device generating a message is a ‘transmitter’, a device receiving is the ‘receiver’. The device that controls the

message is the ‘master’ and the devices which are controlled by the master are the ‘slaves’

Figure 9. System Configuration

The number of data bytes transferred between the START and the STOP conditions from transmitter to receiver is

not limited. Each byte of 8 bits is followed by one acknowledge bit. The acknowledge bit is a HIGH level put on the

bus by the transmitter, 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

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 line during the acknowledge clock pulse so that the SDA line is

stable LOW during the HIGH period of the acknowledge related clock pulse; set-up and hold times must be taken into

account.

A master receiver must signal an end of data to the transmitter by not generating an acknowledge on the last byte

that has been clocked out of the slave. In this event, the transmitter must leave the data line HIGH to enable the master

to generate a STOP condition.

Figure 10. Acknowledgment on I2C Bus