UART RTS CTS signal directions

[mahi]

Hi Community,

I know, there are a lot of threads in this community about this topic, but I could not find a satisfying answer yet. I am currently designing a custom board for i.MX6DL and I am quite confused about the signal directions of the RTS and CTS signal lines of the UART.

By now I thought, the RTS line has the same direction as TXD and CTS the same as RXD, but there are many posts in this forum and also the Processor Expert software claiming the opposite...

For example in this post: i.mx6 uart hardware flow control RTS/CTS the first post mentions the directions as I know them but the answer to this post says they are wrong. Also in i.MX6: What does the DTE/DCE in i.MX6's UART do and how are RTS and CTS affected by the UARTxUFCR[DT... the directions differ from what is written for example in Wikipedia or in various appnotes (e.g. from maxim: RS-232 Features Explained - Application Note - Maxim)...

Can someone please explain to me why there is this discrepancy and how to deal with it?

Best regards,

Martin

[igorpadykov · Accepted solution]

Hi Martin

directions are given Table 89. UART I/O Configuration vs. Mode IMX6SDLCEC

also please look at attached file from imx-test package with its explanations.

Best regards

igor

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[mahi]

Hi Igor,

Thanks for your reply - but I still think the way the directions are defined is pretty weird.

Defining TX as input for DTE mode is really confusing. It seems that the naming of the signals RTS, CTS, DTR, DSR, DCD and RI is derived from their functionality in DTE mode whilst RX and TX are named after their functionality in DCE mode...

Best regards,

Martin