"tried once" hardly constitutes a serious evaluation!


This is one of the key areas where Assembler wins over 'C' without question - 'C' gives you absoultely no control over timing whatsoever!

But how much of your application is really that critical for timing?
It is silly to burden yourself with doing the whole thing in assembler when 'C' would be perfectly suitable for 98% of it!
There is no problem in mixing 'C' and assembler in the same project - as ever, you need to choose the right tool for the job!

BTW: If you're talking about async serial comms, the UART handles all the critical timing - so there is really no need for assembler in that case!