9-bit UART communication for LPC4078

[michelle2022]

Hello,

I am using LPC4078 microcontroller and I need to integrate the UART device which is receiving 9-bit. 

I couldn't find a register that enables 9-bit UART communication in the user manual or library API code.

Does LPC4078 support 9-bit UART comm? If yes, please provide guidance on which register to use.

Thank you

Michelle

[michelle2022]

Hi Edwin,

In addition, I found several points that seem to support 9-bit mode in the document.

Is there a work-around method to transmit 9-bit through UART1 ?

michelle2022_0-1734013983382.png

michelle2022_1-1734014625707.png

Thank you

Michelle

[EdwinHz]

Hi @michelle2022,

The 9th bit in this case is just for the auto address detection feature, not for transmitting 9-bit data size frames. The explanation of this feature is described on section "17.5.21 RS-485/EIA-485 modes of operation" of the User Guide.

BR,
Edwin.

[michelle2022]

Hi Edwin,

Thanks for clarifying.

But, I can see the comment of "9-bit enable" in the RS485CTRL register description for AAD mode.

Could you let me know what it means?

michelle2022_0-1733973281678.png

Thank you

Michelle

[EdwinHz · Accepted solution]

Hi @michelle2022,

Unfortunately, the LPC4078 does not support 9-bit UART communication. As you can see from the "Features" section of each of the UART chapters, the LPC4078's UARTs only support 5, 6, 7, and 8 data sizes.

Sorry for the inconvenience this may cause.

BR,
Edwin.