AD4692BCPZ datasheet(44/81 Pages) AD

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Data Sheet

AD4691/AD4692

DIGITAL INTERFACE

analog.com

Rev. 0 | 44 of 81

CRC Error Detection

The AD4691/AD4692 include SPI transmission error detection for

x8+x2+x+1

(5)

The CRC is enabled by setting the CRC_EN_A and CRC_EN_B

bit fields to 0x1 and 0x2 in the same SPI frame, respectively. Both

bit fields must be written in the same SPI frame to prevent SPI

transaction errors from inadvertently enabling or disabling CRC.

When the CRC is enabled an 8-bit checksum code is appended

to each REG_DATA packet in the data phase, as shown in Figure

74. The checksum calculator applies the CRC-8 polynomial to the

incoming and outgoing REG_DATA packets, allowing the AD4691/

AD4692 to detect transmission errors from the host and vice versa.

Figure 74 and Figure 75 shows the expected CRC checksum code

format for single or multiple register writes and reads per SPI

frame. When CRC is enabled, the AD4691/AD4692 send checksum

codes to the digital host via SDO and validate checksum codes

sent by the digital host via SDI. If the incoming checksum does

not match the expected value, the AD4691/AD4692 assume the

transmission was corrupted; therefore, the internal registers do not

update their values, and the CRC_ERROR bit in the SPI_STATUS

CRC_ERROR bit to detect the occurrence of corrupted data trans-

missions and resulting unexpected device configuration settings.

Table 22 summarizes the data and seed values for the checksum

calculation for all possible register write and read transactions. The

checksum calculation is seeded by a nonzero value to detect if

the SDI input is stuck low. The seed value is 0xA5 for the first

the checksum for each subsequent register is seeded with the

MSByte of the address of that register (for example, 0x0025 for

STD_SEQ_CONFIG, and so on).

Table 22. CRC Calculator Seed and Data Values

Command

CRC Source

First CRC

Subsequent CRCs

Seed Input

Data Input

Seed

Data Source

Write

SDI (from host)

0xA5

R/W, REG_ADDR,

REG_DATA

Current start address

REG_DATA

SDO (to host)

R/W, REG_ADDR,

REG_DATA

Current start address

REG_DATA

Read

SDI (from host)

0xA5

R/W, REG_ADDR, PAD-

DING

Not required, send pad-

ding data

SDO (to host)

R/W, REG_ADDR,

REG_DATA

Current start address

REG_DATA

AD4692BCPZ Datasheet(PDF) 44 Page - Analog Devices

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