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AD7760

Rev. A | Page 32 of 36

Table 13 shows the hexadecimal values (in sign-and-magnitude

format) that are downloaded to the AD7760 to realize this filter.

The table is also split into the bytes that are summed to produce

the checksum. The checksum generated from these coefficients

is 0x0E6B.

Table 13. Filter Hexadecimal Values

Word 1

Word 2

Coefficient

Byte 1

Byte 2

Byte 3

Byte 4

Table 14 lists the 16-bit words the user would write to the

AD7760 to set up the ADC and download this filter, assuming

an output data rate of 1.25 MHz has been selected.

Table 14. Sequence of Write Instructions to Set Up Device

and Download the Filter Example

Word

Description

0x0001

Address of Control Register 1.

0x8079

Control register data. DL filter: set filter length = 24,

set output data rate = 1.25 MHz.

0x032B

First coefficient, Word 1.

0x9688

First coefficient, Word 2.

0x01BF

Second coefficient, Word 1.

0x183C

Second coefficient, Word 2.

…

Other coefficients.

0x0404

Twelfth (final) coefficient, Word 1.

0x3B5F

Final coefficient, Word 2.

0x0E6B

Checksum. Wait (0.5 × tICLK × number of unused

coefficients) for AD7760 to write 0s to the remaining

unused coefficients.

0x0001

Address of control register.

0x0879

Control register data. Set read status and maintain

filter length and decimation settings. Read contents

of status register. Check Bit 7 (DL_OK) to determine

if the filter was downloaded correctly.

AD7760 Datasheet(PDF) 33 Page - Analog Devices

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