TLC6989 datasheet(11/72 Pages) TI1

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7.3.2.1 Command Format

The command format is viewed from the CCSI peripheral side. Figure 7-2 defines the format of the command

transmission. There are three states in one command:

• IDLE: CLK_O is always active and continuous. SIN is always HIGH.

• START: SIN changes from HIGH to LOW after the IDLE state.

• DATA:

– Head_byte: The command identifier, contains one 16-bit data and one check bit.

– Data_bytes_N-1: Each data-byte contains 3 × 17-bit data, each 17-bit data contains one 16-bit data word

and one check bit.

• END: The device recognizes continuous 18-bit HIGH on SIN, and then returns to IDLE state.

• CHECK BIT: The check bit (17th bit) value is the NOT of 16th bit value to avoid continuous 18-bit HIGH (to

distinguish with END).

The IDLE state is not necessary, which means the START state of the next command can connect to the END

state of the current command.

Head_byte

Data_bytes_N

End_bytes

Data_bytes_1

CLK_O

SIN

…...

IDLE START

DATA

END

IDLE

Figure 7-2. Command Format

7.3.2.2 Command Recognition and Synchronization

Two different CCSI commands require at least one END byte in between the commands to be able to be

recognized as separate commands. The TLC6989 automatically inserts one END byte after all the data from

one SPI command has been transmitted. However, for certain CCSI commands, the LED drivers add data to

the data stream. In this case, one END byte during transmission is not sufficient to distinguish the two CCSI

commands by the CCSI peripheral. Without sufficient END bytes, the CCSI controller and CCSI peripheral get

out of synchronization. The synchronization is required for several actions. For example, to determine if the

received data needs to be stored on the RXFIFO or if a CRC needs to be calculated over the received data

and compared to the CRC over the transmitted data. In case the synchronization is lost, the SPI command

SOFTRESET_CRC can be used to bring the CCSI controller and peripheral back in sync. The SPI controller

is responsible there are sufficient END bytes between CCSI commands to keep the synchronization by using a

dedicated SPI command that inserts extra END bytes.

7.3.2.3 CCSI Command Queue

The CCSI controller has the ability to queue multiple SPI commands. This means that when the CCSI controller

is still transmitting, a new SPI forward command can be received by the SPI peripheral. This new command is

automatically transmitted after the old command is finished transmitting. An example is depicted in Figure 7-3.

Note that in this figure every data word is 16 bits. That means that when the width of the block is larger, the clock

frequency is lower. In this example the CCSI frequency is lower than the SPI frequency.

SDI

SDO

SOUT

SPI CMD

Data0

Data1

Data2

CRC0

STATUS

CRC1

Data0

END

SPI CMD

Data3

CRC2

Data1

Data2

STATUS

CRC1

Data3

END

Figure 7-3. Example of queuing CCSI commands

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TLC6989

SLVSHF5 – NOVEMBER 2024

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