WMS7204

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microcontroller by daisy chaining the devices with the SDO of the first device connected to SDI of the

next device as shown in figure 3

FIGURE 3 – DAISY CHAIN CONFIGURATION

A complete command is 24 bits including the instruction and the two data bytes. When shifting 24 bits

in to the first device in the chain, the 24 bits of the previous command will be shifted out. So to set up

two devices in a daisy chain, a total of 48 bits must be sent where the first 24 bits will be shifted out to

the second device and the 24 bits shifted in last will remain in the first device.

FIGURE 4 – DAISY CHAIN COMMAND EXAMPLE

CS

CLK

SDO

SDI SDO

SDI SDO

SDI SDO

Device

Device

Device

Micro

controller

CS

CS

CLK

CLK

CLK

CS

1. Command and data for device 2 is shifted into device 1; this will propagate to Device 2 when

the next 24 bits are shifted in.

Command 1

Data

2

Data

2

xx

xx

xx

Device

Device

2. Command and data for device 1 is shifted into device 1. Now Device 1 and 2 are correctly set

up

Command 2

Data

1

Data

1

Command A

Data

2

Data

2

Device

Device