STM32H743 sysclk and Ethernet

[ingdb]

Hello all,

I have a project with ethernet on custom STM32H743 board, ethernet works as expected but only with SYSCLK <= 300 MHz, for sysclk > 300 MHz I get "transmit buffer unavailable" messages.

Even when reducing the HCLK, AXI, AHB bus clock, the system still does not work. It looks like the only problem is the sysclk frequency. I googled a lot but did not find any explanation, it is related to the DMA transmit buffer but why is this dependent on the SYSCLK.

Here's a working clock configuration:

 

Regards.

Matthias

 

[Pavel A.]

> it is related to the DMA transmit buffer

I wouldn't be so sure. Custom board, custom PHY.

Need to run a low-level test, such as raw packet sending without any tcp/ip stack. Unfortunately ST does not provide such tests.