KTB8331

December 2021

– Revision 04b

Page 16 of 25

Kinetic Confidential

I2C Read Cycle

For I2C read cycle, data is transferred from a slave to a master. But to start the read cycle, master needs to write

the register address first to define which register data to read. Figure 4 shows the steps of the I2C read cycle.

Figure 4. I2C Read Cycle

I2C Read Cycle Steps:

• Master generates start condition.

• Master sends 7-bit slave address and 1-bit data direction ‘0’ for write.

• Slave sends acknowledge if the slave address is matched.

• Master sends 8-bit register address.

• Slave sends acknowledge.

• Master generates repeated start condition.

• Master sends 7-bit slave address and 1-bit data direction ‘1’ for read.

• Slave sends acknowledge if the slave address is matched.

• Slave sends the data byte of that addressed register.

• If master sends acknowledge, the register address will be incremented by one after each acknowledge and the

slave will continue to send the data for the updated addressed register.

• If master sends no acknowledge, the slave will stop sending the data.

• Master generate stop condition to finish the read cycle.

Rs

Device Address

1

A

P

‘1’

Read

7 bits

8 bits

S

Device Address

Register Address

0

A

A

‘0’

Write

7 bits

8 bits

Data

A*

From Slave to Master

From Master to Slave

S = Start

Rs = Repeated Start

A = Acknowledge (SDA Low)

A* = No Acknowledge (SDA High)

P = Stop