SC900 Datasheet, PDF (14/23 Pages) Semtech Corporation – Programmable Penta ULDO with RESET and I2C Interface

SC900
POWER MANAGEMENT
Applications Information (Cont.)
Supported Formats
Direct Format - Write
The simplest format for an I²C write is the direct format. After the start condition [S], the slave address is sent,
followed by an eighth bit indicating a write. The SC900 I²C then 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 appropriate 8-bit data byte. Once again the slave acknowledges and the master terminates the
transfer with the stop condition [P].
I²C Direct Format - Write
S Slave Address W A
Register Address
A
Data
AP
S : Start Condition
W: Write = '0'
A : Acknowledge (sent by slave)
Sr: Repeated Start Condition
P : Stop Condition
Slave Address : 7 bit
Register Address : 8 bit
Data : 8 Bit
Combined Format - Read
After the start condition [S], the slave address is sent, followed by an eighth bit indicating a write. The SC900 I²C
then 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 address 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].
I²C Combined Format - Read
S Slave Address W A
Register Address A Sr Slave Address R A
S : Start Condition
W: Write = '0'
R : Read = '1'
A : Acknowledge (Sent by Slave)
B : Acknowledge (Sent by Master)
Sr: Repeated Start Condition
P : Stop Condition
Slave Address : 7 bit
Register Address : 8 bit
Data : 8 Bit
Data
BP
 2005 Semtech Corp.
14
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