23-02-2013, 12:16 PM
Real-Time Operating Systems
Real-Time Operating Systems.pdf (Size: 198.37 KB / Downloads: 18)
What’s an Operating System?
Provides environment for executing programs
Process abstraction for multitasking/concurrency
• Scheduling
Hardware abstraction layer (device drivers)
Filesystems
Communication
We will focus on concurrent, real-time issues
Cyclic Executive
Advantages
• Simple implementation
• Low overhead
• Very predictable
Disadvantages
• Can’t handle sporadic events
• Everything must operate in lockstep
• Code must be scheduled manually
Interrupts
Some events can’t wait for next loop iteration
• Communication channels
• Transient events
A solution: Cyclic executive plus interrupt routines
Interrupt: environmental event that demands
attention
• Example: “byte arrived” interrupt on serial channel
Interrupt routine: piece of code executed in response
to an interrupt