At run-time my ETH_MACDBGR register samples always come back zero for all 32 bits. Does it require some enable bit to be set, or some idiom for when to read it? This is on an STM32F746G Disco.

[TDK]

You need to initialize and use the peripheral before any of those flags in that register are going to be set. Why do you think it should be non-zero?

[PDR]

I'm polling that register and several others while sending and receiving packets, for example the counts of good frames transmitted, good unicast frames received, frames missed, the status bits of RDES0, and so on. So I expected to see some of the bits in MACDBGR changing, but I have no prior experience with this register.