Is the CAN bus software or hardware?

Is the CAN bus software implemented (i.e. uses cpu cycles to send and receive data) or hardware (i.e. is using the chip’s abilities natively).

CAN can’t be implemented in software. It is very complex and sensitive… And patented!

it’s still patented? I thought that expired in the early 2000’s

From my reading the gist is that, messages come in while the CPU is doing other things; handled by the CAN subsystem. The CPU then has to check if there are any messages or does it generate an interrupt? Also, what is the max size of a mailbox, and how many mailboxes do the Cerb family devices have?

EDIT: NVMD :slight_smile: