4 ms·
> Start with MMC clock frequency at 52 MHz instaed of 400 kHz. Whoa there! Spec violation. Not guaranteed to work. Might work some days but not others.
by dmitrygr 6y ago
> Start with MMC clock frequency at 52 MHz instaed of 400 kHz.
Whoa there!
Spec violation. Not guaranteed to work. Might work some days but not others.
- eerimoq 6y agoThe goal is to not configure the MMC at all in Linux, but just rely on the bootloader has already configured it. Btw, where can I find the spec? And where in the spec can I read about this? Is this true even if we know the MMC supports 52 MHz?
- dmitrygr 6y agoSpec says initialization shall be done at 400KHz or less. You can Google for sd spec
- eerimoq 6y agoWill fix it at some point =)
- OnACoffeeBreak 6y agohttps://www.jedec.org/sites/default/files/docs/JESD84-B451.pdf https://www.jedec.org/sites/default/files/docs/JESD84-B451.p... You can use http://bugmenot.com/view/jedec.org http://bugmenot.com/view/jedec.org to get free-to-use credentials. The section in point is "A.6.1Bus initialization". I'd say that if your MMC works fine going full-speed out of the gate and the IC on the board supports this speed, then you unlikely to encounter any issues.
- eerimoq 6y agoThank you very much. Very helpful answer. I'll continue to use 52 MHz until I encounter problems (if any).