SC622A データシートの表示（PDF） - Semtech Corporation

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SC622A

LED Light Management Unit Charge Pump, 400mA Flash LED, Dual LDOs, and I2C Interface

Semtech Corporation 

SC622A

Serial Interface

The I2C General Specification

The SC622A is a read-write slave-mode I2C device and

complies with the Philips I2C standard Version 2.1, dated

January 2000. The SC622A has four user-accessible

internal 8-bit registers. The I2C interface has been

designed for program flexibility, supporting direct format

for write operation. Read operations are supported on

both combined format and stop separated format. While

there is no auto increment/decrement capability in the

SC622A I2C logic, a tight software loop can be designed

to randomly access the next register independent of

which register you begin accessing. The start and stop

commands frame the data-packet and the repeat start

condition is allowed if necessary.

SC622A Limitations to the I2C Specifications

The SC622A only recognizes seven bit addressing. This

means that ten bit addressing and CBUS communication

are not compatible. The device can operate in either

standard mode (100kbit/s) or fast mode (400kbit/s).

by an eighth bit indicating a write. The SC622A 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].

Combined Format — Read

After the start condition [S], the slave address is sent,

followed by an eighth bit indicating a write. The SC622A

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].

Slave Address Assignment

The seven bit slave address is 0110 111x. The eighth bit is

the data direction bit. 0x6E is used for a write operation,

and 0x6F is used for a read operation.

Supported Formats

The supported formats are described in the following

subsections.

Direct Format — Write

The simplest format for an I2C write is direct format. After

the start condition [S], the slave address is sent, followed

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 SC622A

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 SC622A with

a read command. The device acknowledges this request

and returns the data from the register location that had

previously been set up.

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