topic Re: Flow control signals direction on i.MX6 in i.MX Processors

Flow control signals direction on i.MX6

xinjian1 — Thu, 15 Jun 2023 01:27:17 GMT

We are working on i.MX6UL with Bluetooth module, we need to use flow control of UART, but the RTS and CTS direction seems incorrect, we swapped those two signals then works.

Here is the definition/direction of signals on i.MX6UL reference manual:

for my understanding, the direction of RTS (request to send) should be always the same as TX, like the signal descriptions on i.MX8 manual:

Please clarify, which one is correct?

Thanks.

Re: Flow control signals direction on i.MX6

joanxie — Thu, 15 Jun 2023 03:02:41 GMT

pls refer to the document as below

"https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/i-MX6-What-does-the-DTE-DCE-in-i-MX6-s-UART-do-and-how-are-RTS/ta-p/1105540"

Re: Flow control signals direction on i.MX6

xinjian1 — Thu, 15 Jun 2023 03:45:15 GMT

Thanks for your quick reply.

From this web page: https://en.wikipedia.org/wiki/RS-232#RTS,_CTS,_and_RTR

The definition of RTS is: "DTE requests the DCE prepare to transmit data."

The definition of TXD is: "Carries data from DTE to DCE."

By the above definitions, the direction of TXD and RTS should be the same, either on DTE mode or DCE mode.

We can see on i.MX6UL reference manual, the direction of RTS is not the same and TXD, but on i.MX8 manual, the direction of RTS is the same as TXD.

Question is, which one is correct?

Re: Flow control signals direction on i.MX6

joanxie — Thu, 15 Jun 2023 09:02:36 GMT

I couldn't open this link, pls refer to the link I sent to you, it's very clear to explain this, and you can download document from the link too

Re: Flow control signals direction on i.MX6

xinjian1 — Thu, 15 Jun 2023 22:45:42 GMT

This is the table from the link, the RTS is always the same direction as TXD, and CTS is opposite.