TLC6989 datasheet(24/72 Pages) TI1

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7.5.3 SPI Command Format

Figure 7-9 and Table 7-2 define the format of the SPI command transmission. Each SPI command contains

multiple 16-bit words. The different types of words are:

• Command word: The command word always includes an identifier of the command type. Dependent on the

type, the command word also includes:

– Start address to be written or read. When field address = 0 means address 0x00.

– Length of the data that is transmitted or expected to be read. When the length field starts with opt, the

data is optional. Therefore, opt_data_length = 0 means 0 data words. For fields that do not start with opt,

data_length = 0 means 1 data word.

– Number of extra END bytes to append when forwarding data. When field extra_end_bytes = 0 means 0

additional END bytes. A maximum of 127 extra END bytes can be appended with one SPI command.

– Fixed data (in case of SOFTRESET_CRC command)

• Data word: Dependent of the command type this is data that needs to be forwarded (0 to N), register data

that is written to (0 to N) or read from (N+1 to M) the device, or data read from (N+1 to M) the RXFIFO.

• CRC word: There are 2 different CRC words in each command:

– CRC word that is generated by the SPI controller. This CRC is calculated over the SPI command word

and all transmitted data words (0 to N)

– CRC word that is generated by the SPI peripheral. This CRC is calculated over all the returned data words

(N+1 to M).

Two different CRC algorithms are supported. The default algorithm is CCITT-FALSE. This can be changed to

the CRC-16/XMODEM algorithm using the REG_WR command. After changing the CRC algorithm, the next

SPI command uses the new algorithm. Both algorithms are based on the polynomial X16 + X12 + X5 + 1.

CRC word 0

SDI

…...

Data word N

Data word 0

Command word

SCLK

SDO

…...

CRC word 1

…...

Data word M

Data word N+1

Figure 7-9. SPI Command Format

TLC6989

SLVSHF5 – NOVEMBER 2024

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TLC6989 Datasheet(PDF) 24 Page - Texas Instruments