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POWER MANAGEMENT

SC905

Slave Address

Register Address

Data

S

W A

AA P

S: Start Condition

Slave Address: 7 bit

W: Write = ‘0’

Register Address: 8 bit

A: Acknowledge (sent by slave)

Data: 8 bit

P: Stop condition

I

Combined Format - Read

acknowledges that it is being addressed, and the master responds with an 8 bit data byte consisting of the register

address. The slave acknowledges and the master sends the repeated start condition [Sr]. Once again, the slave ad-

dress is sent, followed by an eighth bit indicating a read. The slave responds with an acknowledge and the previously

addressed 8 bit data byte; the master then sends a non-acknowledge (NACK). Finally, the master terminates the transfer

with the stop condition [P].

Slave Address

Register Address

Slave Address

Data

NACK

S

W A

A Sr

R A

P

S: Start Condition

Slave Address: 7 bit

W: Write = ‘0’

Register Address: 8 bit

R: Read = ‘1’

Data: 8 bit

A: Acknowledge (sent by slave)

NACK: Non-Acknowledge (sent by master)

Sr: Repeated Start Condition

P: Stop condition

I

Slave Address

Register Address

Slave Address B

Data

NACK

S

W A

A

S/Sr

R A

P

P

Slave Address A

S

S: Start Condition

Slave Address: 7 bit

W: Write = ‘0’

Register Address: 8 bit

R: Read = ‘1’

Data: 8 bit

A: Acknowledge (sent by slave)

NACK: Non-Acknowledge (sent by master)

Sr: Repeated Start Condition

P: Stop condition

I

Register Address Setup Access

Master Addresses

other Slaves

Register Read Access

Stop Separated Reads

Stop-separated reads can also be used. This format allows a master to set up the register address pointer for a read

and return to that slave at a later time to read the data. In this format the slave address followed by a write command

are sent after a start [S] condition. The SC905 then acknowledges it is being addressed, and the master responds

with the 8-bit register address. The master sends a stop or restart condition and may then address another slave.

After performing other tasks, the master can send a start or restart condition to the SC905 with a read command.