7.2 Peripheral Supplementary From the view of OS to see interrupt

Reference Silberschatz, Galvin, Gagne, “Operating System Concepts (sixth edition)”, John Wiley and Sons, INC

Interrupt-driven system The OS may support the interrupt requests to control the devices of the system

Interrupt Driven System If there are no processes to execute, no I/O devices to service, and no users to whom to respond, Then, an OS will sit quietly, waiting for something to happen. Events are almost always signaled by the occurrence of an interrupt or a trap(or exception), which is a software- generated interrupt caused either by an error or by a specific request from a user program.

Interrupt-driven system The occurrence of an event is usually signaled by an interrupt from either the hardware or the software. Hardware (device) may trigger an interrupt at any time by sending a signal to the CPU usually by system bus. Software may trigger an interrupt by executing a special operation called a system call.

Device-status table In OS aspect, it is necessary to handle those I/O devices currently. The OS uses a table contain an entry for each I/O device. Each table entry indicates the device’s type, address, and state (functioning, idle or busy)

Device-status table Device 1 Status Request for laser printer Address: Length: 1234 Device 4 Status Device 2 Status Device 3 Status Request for disk1 File:XXX Operation: read Address: 123 Length:333 Request for disk1 File:XXX Operation: write Address: 123 Length:333