AD7280ABSTZ datasheet(41/48 Pages) AD

41 / 48 page

AD7280A

Rev. 0 | Page 41 of 48

Example 4: Convert and Read a Single Voltage

or Auxiliary ADC Input Result from One Part

In this example, it is assumed that all AD7280As in the daisy

chain have been initialized to their correct device addresses.

The register address corresponding to the voltage or

auxiliary ADC input result to be read should be written to

the read register of the part to be read (see Table 13 for

write command is 0xC382865A (see Table 26, Write 1).

Set Bits[D13:D12] of the control register to 1 on all parts.

This setting turns off the read operation on all parts. The

32-bit write command is 0x01B617EA (see Table 26,

Write 2).

Set Bits[D13:D12] of the control register of the part to be

read from such that the required voltage is read back. With

the exception of a self-test conversion, it is not possible to

convert on a single channel; six, nine, or 12 conversions must

be completed. This example reads a voltage conversion from

Device 3 in the stack; therefore, Bit D14 and Bit D12 of the

control register should be set to 0, and Bit D15 and Bit D13

should be set to 1 on Device 3. The 32-bit write command

is 0xC1B400FA (see Table 26, Write 3).

Program the CNVST control register to 0x02 on Device 3

to allow conversions to be initiated using the CNVST pin

on that part. The 32-bit write command is 0xC3A0417A

(see

, Write 4).

Table 26

Initiate conversions through the falling edge of CNVST.

Allow sufficient time for all conversions to be completed

plus tWAIT.

Program the CNVST control register to gate the CNVST

signal on all parts. The 32-bit write command is

0x03A0340A (see

, Write 5). This write prevents

unintentional conversions from being initiated by noise or

glitches on the

Table 26

CNVST pin. This write also updates the on-

chip output registers of all devices in the daisy chain.

Apply a CS low pulse that frames 32 SCLKs to read back

the desired voltage or auxiliary ADC result. This frame

should simultaneously write the 32-bit command

0xF800030A, as described in the

section

(see

, Write 6).

Serial Interface

Table 26

Note that when reading from a single device in a stack of

AD7280As, the SCLK frequency must be lower than 1 MHz

to read back the register data from parts higher in the chain

than the master device.

Table 26. Example 4: Converting and Reading a Single Voltage or Auxiliary ADC Result from One AD7280A Device

Write Command

Device Address

Data

Write All

D11

8-Bit CRC

D2 to D0

32-Bit Write

Command

Write 1

11000

011100

00010100

11001011

010

0xC382865A

Write 2

00000

001101

10110000

11111101

010

0x01B617EA

Write 3

11000

001101

10100000

00011111

010

0xC1B400FA

Write 4

11000

011101

00000010

10000111

010

0xC3A0417A

Write 5

00000

011101

00000001

10000001

010

0x03A0340A

Write 6

11111

000000

00000000

01100001

010

0xF800030A

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