Depends on what you mean be "detected":

If you mean, that something is done automatically "behind" the execution of instructions of program, like it's done when an interrupt is invoked, then no.

But if you mean, that it can be detected somehow, by the execution of a suited instruction as part of program, then yes. In this case you can use a mov-instruction to move the actual state of involved port line into the carry bit, for instance. Or you can read the whole 8bit port.

But take care: There's no latch, which stores the pulling down of port line anyhow! You can only read the actual state being present at port pin during the execution of mov-instruction. So, if you read the port pin not often enough you can easily overlook the pulling down of port line! That's why this interrupt methode is often used.

Reading a certain port pin all the time in order to detect a change of state is called "polling", by the way.

Kai