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STM32F746 FMC NWE periodically goes high


Hello. I'm using STM32F745VET.

I want to connect SRAM via FMC, but when I run a simple app, the waveform look like below.


The code I made is just write data "0x28". and It does not work.

As you see, NWE signal work high-low periodically. I think this is the problem why data failed to write to SRAM.

Is there any idea why NWE works like that?


I'm not sure why a single write would generate multiple write pulses, but generally, the Cortex M7 core is very complicated, including caches, and reads and writes are far from being simple and straighforward.

Start with setting the FMC area as Device in MPU, or use remap if it's available and sets the desired area as Device without setting in MPU.


Associate II

Hi @Kourinho,

Just my 2p worth, but it looks like your NWE is set to be active low. The changes of value from '0' to '1' look like the end of access. Could you post your code that you are using to achieve this wave form? It sort of looks like you are accessing a long word (32bits) thats being cut up into 2-16 bit accesses.

Show us your code...


ST Employee


Please post the code that reproduces the behavior so we can help you.


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