AS3722 datasheet(79/198 Pages) AMSCO

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ams Datasheet

Page 79

[v1-01] 2015-Sep-07

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AS3722 − Detailed Descriptions- System Functions

Serial Control Interfaces

AS3722 features an I2C and SPI interface. Both interfaces are

sharing the same pins and can therefore not be used at the same

time.

Figure 72:

I2C-SPI Block Diagram

I2C-SPI Block Diagram: Shows the internal structure and connections between the I2C and SPI interface.

I2C-SPI Mode Selection

The AS3722 provides automatic selection of serial interface

modes SPI and I2C. I2C/SPI configuration is chosen by the SPI

chip select pin SCSB. Initially after power-on-reset the chip is in

I2C mode. As soon as SCSB goes high for more than 1ms (with

an internal de-bouncer in MODE DEDECT block), the device

switches to SPI mode and stays in SPI mode till the next reset.

For SPI that means that the interface must go inactive (high) for

>1ms before the first SPI access can be done.

For I2C mode operation the device pin SCSB must always be

connected to ground.

Figure 73:

I2C-SPI Mode Selection

I2C-SPI Mode Selection: Shows the state diagram on how to change between the I2C and SPI interface.

SDA/SDI

SPI

SCL/SCLK

SDO

SCSB

I2C

VDD_GPIO_lv

1.5 … 3.6V

MODE

DETECT

V2_5

mode

For I2C mode,

PIN SCSB must be

grounded externally.

I2C mode

SPI mode

POR

SCSB==1 for > 1ms

RESET_N==0

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