Is there any way to write to the address 0x3B000E (OS Certificate, name of calculator)?
I can read from it, but writing to it has no effect.
I know that it is possible, because CERMASTR does it to change the name of the calculator.

Code:

https://wikiti.brandonw.net/index.php?title=84PCE:Syscalls:0002E0
Make sure to do your research on this first; else you may brick your calculator.

Umm . . . I have no clue what any of that means :/

EDIT:
I get it in an ASM sense, but how do I use it in C?

What are you trying to do? Just change the calc name from a program?

If you just want to write bytes to the memory address 0x3B000E, beck is correct, you'll have to use the OS flash erase sector and write routines because that address is in flash.

However, if you want to change the calc name, simply writing to that address probably isn't the correct way to do it. The certificate is made of fields that are formatted in a particular way. As a result, the calc name might not be in the same memory location on different calcs, depending on the OS version and whether the user has modified their certificate with CERMASTR. Also, writing a name longer than the old one would overwrite the next field, so you would have to shift the other fields over.

I just looked into CERMASTR, and it looks like it copies the certificate to RAM, parses and modifies it, then writes the entire page back to its original location. It also parses the fields, which are documented here.

You can call assembly functions from C using this tutorial, which Mateo so generously named after me: https://github.com/CE-Programming/toolchain/wiki/FAQ#commandz-stupid