STM32L452CC and STM32L4Q5CGU6, issue with USART

[Riscy00_UPP]

My colleagues went to my office and reported that the STM32L452CC with the USART interface (5MHz and 10MHz) was working fine but had to use STM32L4Q5CG due to stock usage, but it failed at 10MHz but working fine 5MHz.

I have explored errata, datasheet and reference manual (L452 and L4Q5), and I don't see anything obvious to explain why 10MHz USART (in UART mode via RS485 transceiver) is not working on STM32L4Q5CG.I wonder if you may shed some light on what to look for in the firmware that is causing this issue or if something is missing from Errata.

Thanks

[Tesla DeLorean]

Not working is a bit non-specific.

What is happening? Getting some data? Scope or Logic Analyzer can see correct data, at correct frequency? Problem receiving or transmitting?

Clocking the parts / buses differently? What frequencies?

[Riscy00_UPP]

Yes it is non-specific,I was hoping for some pinpointing of what actual changes between MCU of the very same specs under the same reference manuals, that stop 10MHz from working.

[Tesla DeLorean]

Ones an L4 at 80 MHz, the other is an L4+ at 120 MHz, so different die for sure.

Probably different IRQ and DMA relationships.

Going to need to isolate what aspects are and are not functioning