Two things connected in a way that cannot be modified by
software are hard wired. See also
hard code (but that applies to software, where this usually applies to
hardware).
Up until recently, making things "hard wired" was the only way to design electronics, until FPGAs and other on-board and self-programmable devices came into the market.
Note: Oops! It was just pointed out to me that some people write it as hardwired.