ADEMA124 datasheet(32/78 Pages) AD

32 / 78 page

Data Sheet

ADEMA124/ADEMA127

APPLICATIONS INFORMATION

analog.com

Rev. A | 32 of 78

Daisy-Chain

The bidirectional, serial port interface (SPI) supports a daisy-chain

connection, which allows access to all registers while reducing

the required microcontroller pin count. In the case of the SPI daisy-

chain configuration, the CS signals from all connected devices are

shared.

Daisy-chain devices function as successive shift registers. In the

example configuration of Figure 56, data is shifted out of the micro-

controller to the ADEMA127, then to the ADEMA124, and finally the

ADE9113. The instant CS transitions from low-to-high, the portion

of the SPI frame contained in the shift register of each device

is interpreted. The example communications bit stream shown in

Figure 57 corresponds with the example circuit in Figure 56.

The ADEMA124/ADEMA127 register configuration is not required

for daisy-chain connected devices, however, SPI long frame format

shown in Long Format Operation must be used for communication.

The full SPI frame for daisy-chain connected devices must be

the sum of all long format packets for all devices connected in

daisy-chain.

Daisy-chain connected devices must operate from the same clock

source. The clock source may be external, or it may be generated

by the ADEMA124/ADEMA127 and shared via CLKOUT pin. Only

a single DREADY pin is required for the daisy-chain to call for

service. For more details on synchronization of sampling, see the

Synchronization of Multiple Devices section.

Figure 56. Daisy-Chain Connected Devices Example

Figure 57. Daisy-Chain Communication Example

Individually Addressed

Individually addressed devices may be issued both short and long

format commands.

ADEMA124 Datasheet(PDF) 32 Page - Analog Devices