AS3695C

austriamicrosystems

www.austriamicrosystems.com

Rev 1.11 / 2010-12-08

25 - 39

5

SPI interface

For the data transfer a serial peripheral interface (SPI) is used. The SPI is configured to work only as

SPI slave. If more than one driver is connected to a SPI master, they can be connected in a “Daisy

Chain”-structure or a parallel structure.

5.1

SPI daisy-chain structure

All SPI slaves share the same clock (SCLK) and chip select (xCS ) signal. In that configuration all

devices can be treated as one big shift register. The devices are automatically enumerated as described

in the next section.

5.2

SPI parallel structure

All SPI slaves share the same input (SDI) output (SDO) and clock (SCLK) signal. Every single device

can be addressed via the chip select ( xCS ) signal. In this configuration every device has

DevAddr = 0x01.

5.3

SPI device address enumeration

The device address of each driver is automatically set by the position of the device in the chain.

The first device has DevAddr = 0x01, the second device has DevAddr = 0x02 and so on. Device

Addresses 0x00 and 0x3F are used for special broadcast writing commands described below.

MOSI

MISO

SCLK

xCS

SCLK

xCS

SDI

SDO

Micro

Controller

Master

Dev1

SCLK

xCS

SDI

SDO

Dev2

SCLK

xCS

SDI

SDO

DevN

MOSI

MISO

SCLK

xCS_N

SCLK

xCS

SDI

SDO

Micro

Controller

Master

Dev1

SCLK

xCS

SDI

SDO

Dev1

SCLK

xCS

SDI

SDO

Dev1

xCS_2

xCS_1