Posted on August 16, 2016 at 06:21What Clive is avoiding saying out loud, but everybody else is screaming is ''just use C!''
The ARM processors, like all RISC processors is designed to be used in conjunction with compilers. You
can use assembly, but it isn't recommended, especially with a processor as complex as an ARM. Your time is better used learning the architecture from a book rather than putting together the grains of sand that is assembly code.
Other processors have been more amenable to writing assembly code, like the National Semiconductor 32000 line, but with good compilers, there just isn't much point in making processors that are programmed by hand anymore, and these processors have died out. Assembly writing is too slow and the optimizing compilers are too good.
Getting a processor started, from boot, is not where you should be learning an architecture. That is like learning building design by implementing New York's Guggenheim museum. You have far greater things to worry about, like starting the clocks, finding the device registers in the 4.2billion possible memory locations, and getting an LED blinking.
Asking if you need the vector table tells me that you haven't looked at the interrupt section of the book yet. Clive is being very generous by telling you that you don't
need the vector table, but the processor
is expecting it to be there, and if anything goes wrong, and it will, the processor
will go to where the vector table should be, pick up your code and interpret it as an address, then generate another interrupt when that address is bogus, and repeat until you recognize that you've done something wrong. The startup files that come with your compiler take care of a zillion details that are completely arcane, easy to get wrong, and really don't need a rewrite, just use them.
What should you do? Let's see, read this: http://embedded.fm/blog/2016/2/25/do-i-need-to-know-assembly-language-to-write-c-well
Then start here: http://embedded.fm/blog/2016/2/16/embedded-software-engineering-101-introduction
I'm starting a new blog series dealing with getting started with the STM32F407 in particular, but the knowledge is very transferable to any ST ARM. Take a look at the rest of the work on embedded.fm, step away from the assembler, and grab your compiler.
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