DAC61402 datasheet(32/54 Pages) TI

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8.5.2 Daisy-Chain Operation

For systems that contain several devices, the SDO pin can be used to daisy-chain the devices together.

Daisy-chain operation is useful in reducing the number of serial interface lines.The SDO pin must be enabled by

setting the SDO-EN bit before initiating daisy-chain operation.

The first falling edge on the SYNC pin starts the operation cycle (see Figure 8-4). If more than 24 clock pulses

are applied while the SYNC pin is kept low, the data ripple out of the shift register and are clocked out on

the SDO pin, either on the falling edge or rising edge of SCLK according to the FSDO bit. By connecting the

SDO output of the first device to the SDIN input of the next device in the chain, a multiple-device interface is

constructed.

Each device in the daisy-chain system requires 24 clock pulses. As a result the total number of clock cycles

must be equal to 24 × N, where N is the total number of devices in the daisy chain. When the serial transfer to all

devices is complete, the SYNC signal is taken high. This action transfers the data from the SPI shift registers to

the internal register of each device in the daisy chain, and prevents any further data from being clocked into the

input shift register.

D23

D16

D15

Device A command

SYNC

SCLK

SDIN

SDO

D23 ± D1

Device B command

D23 ± D1

NOP

Device A command

Device B command

Figure 8-4. Serial Interface Daisy-Chain Write Cycle

DAC81402, DAC61402

SLASEH3A – OCTOBER 2020 – REVISED MAY 2021

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DAC61402 Datasheet(PDF) 32 Page - Texas Instruments