Clarification on RTS/CTS Mapping on i.MX93

[hamzaatifi]

Hello,

I am working with UART on both i.MX93 and i.MX8M Plus and facing an issue with RTS/CTS connections.

On i.MX93, the following wiring works correctly:

• TX  → RX (RS232)
• RX  ← TX (RS232)
• CTS  → RTS (RS232)
• RTS  ← CTS (RS232)

However, on i.MX8M Plus, this wiring does not work. It only works if I swap RTS and CTS.

Additionally, I noticed that the Reference Manual for both i.MX93 and i.MX8M Plus states:

• CTS_B = Input (i.MX93)
• RTS_B = Output (i.MX93)

• CTS_B = Output (i.MX8M Plus in DCE)
• RTS_B = Input (i.MX8M Plus in DCE)

But in the Pinmux config tool 24.12 I see:

• CTS_B as Output (i.MX93)
• RTS_B as Input (i.MX93)

• CTS_B as Input (i.MX8M Plus in DCE)
• RTS_B as Output(i.MX8M Plus in DCE)

My questions:

1. Is the RTS/CTS mapping on i.MX8M Plus different from i.MX93?
2. Is there a known discrepancy between the Pinmux tool and the Reference Manual?

I appreciate any clarification on this issue.

Thanks in advance!

Best regards,
Hamza

[danielchen · Accepted solution]

Hi @hamzaatifi 

1 ) According to i.MX93 RM,  RTS is output and CTS is input.  while in iMX8MP RM,  CTS is output and RTS is input.  They are using different naming conventions.

2) Unfortunately, the direction in config tools for both SOCs are inverted.  An internal ticket was created for this.  

Thank you very much for your feedback.

Regards

Daniel 

Regards

Daniel

[danielchen]

Hi  Hamza

Let me check it  on my side,  will get it back to you once I have any results.

Regards

Daniel

[hamzaatifi]

Hi @danielchen,

After updating to the latest MCUXpresso config tools v25.06, we noticed an inconsistency regarding the CTS/RTS pin directions on the i.MX93:

• In the Routing Details window, the directions are now correct (CTS = input, RTS = output).

• However, if you hover over the muxing options in the Pin List, the directions are still shown incorrectly.

 

This makes the tool internally inconsistent for the i.MX93.

Could you please confirm if this is a known issue, and whether it will be addressed in a future release?

Hamza