AD7381 datasheet(23/31 Pages) AD

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Data Sheet

AD7380-4

Rev. 0 | Page 23 of 31

READING FROM DEVICE REGISTERS

All registers in the device can be read over the serial interface. A

followed by an additional SPI command that can be either a

valid command or no operation command (NOP). The format

for a read command is shown in Table 16. Bit D15 must be set

to 0 to select a read command. Bits[D14:D12] contain the

ignored.

WRITING TO DEVICE REGISTERS

All the read/write registers in the AD7380-4 can be written to

over the serial interface. The length of a SPI write access is

determined by the CRC write function. An SPI access is 16 bits

if CRC write is disabled and 24 bits when CRC write is enabled.

The format for a write command is shown in Table 16. Bit D15

must be set to 1 to select a write command. Bits[D14:D12]

contain the register address. The subsequent 12 bits, Bits[D11:D0],

contain the data to be written to the selected register.

CRC

The AD7380-4 has CRC checksum modes that can be used to

improve interface robustness by detecting errors in data

transmissions. The CRC feature is independently selectable for

SPI interface reads and writes. For example, enable the CRC

function for SPI writes to prevent unexpected changes to the

device configuration but do not enable it on SPI reads to maintain

a higher throughput rate. The CRC feature is controlled by

programming of the CRC_W bit and CRC_R bit in the

CONFIGURATION1 register.

CRC Read

If enabled, a CRC consisting of an 8-bit word is appended to the

conversion result or register reads. The CRC is calculated on the

conversion result for ADC A, ADC B, ADC C, and ADC D, and

is output on SDOA. A CRC is also calculated and appended to

The CRC read function can be used in 2-wire SPI mode, 1-wire

SPI mode, 4-wire SPI mode, and resolution boost mode.

SDI

SDOA

RESULT S0

REG1 DATA

REG 2 DATA

RESULT S3

INVALID

RESULT S0

INVALID

READ REG1

READ REG2

NOP

RESULT S3

SDOB,

SDOC,

SDOD

Figure 41. Register Read

SDI

SDOx

RESULT S0

RESULT S1

RESULT S2

INVALID

WRITE REG 1

WRITE REG 2

NOP

Figure 42. Register Write

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