interrupt service routine (ISR)

Interrupt service routines ( ISR) are then processed by the microprocessor as soon as an interrupt occurs.

An ISR routine can record information and execute basic instructions before the interrupt is acknowledged and the operating system returns to the control process.

The time between a device interrupt request and the first command of the corresponding ISR routine is called interrupt latency. The time between an interrupt request and the first command of the activated thread is called Thread Response Time.

These times play an essential role in real-time operating systems, since the interrupts must be processed as quickly as possible.