These are syscalls used for higher level communication using Protocol 7.00 or similar, through the 3-pin serial port or USB. Most are related to the built-in “Link” app.

For lower level communication through the 3-pin serial port, that is not bound to a specific protocol, see the Serial category. Note that some of the syscalls in this category are a plain wrapper around the Serial syscalls, but only if the chosen channel is the serial port.