Question

In: Computer Science

What is the purpose of the CLI and SEI instructions? What do they do, and what...

What is the purpose of the CLI and SEI instructions? What do they do, and what are they used for in a typical program?

Solutions

Expert Solution

CLI: Clear interrupt flag; interrupts disabled when interrupt flag cleared.

CLI is commonly used as a synchronization mechanism in uniprocessor systems. For example, a CLI is used in operating systems to disable interrupts so kernel code (typically a driver) can avoid race conditions with an interrupt handler.

If protected-mode virtual interrupts are not enabled, CLI clears the IF flag in the EFLAGS register. No other flags are affected. Clearing the IF flag causes the processor to ignore maskable external interrupts. The IF flag and the CLI and STI instruction have no effect on the generation of exceptions and NMI interrupts.

When protected-mode virtual interrupts are enabled, CPL is 3, and IOPL is less than 3; CLI clears the VIF flag in the EFLAGS register, leaving IF unaffected

SEI - Set Global Interrupt Flag

Sets the Global Interrupt flag in SREG (status register). The instruction following SEI will be executed before any pending interrupts.


Related Solutions

what purpose do fimbrae serve?
what purpose do fimbrae serve?
What is an effective SEI strategy used in the classroom? Why does this strategy work? Does...
What is an effective SEI strategy used in the classroom? Why does this strategy work? Does these teaching concepts tie to the students background?
1) The set of instructions that tells a computer what to do is called a ______________?...
1) The set of instructions that tells a computer what to do is called a ______________? 2) A program design tool used to list the attributes and methods of objects within an object-oriented program is called _______________. 3) Of the programming languages discussed in the textbook, which language is used to create web applications (called applets) that can be inserted into web pages? 4) If a programmer makes a spelling mistake or violates the rules of the programming language the...
What is the purpose of a marketing plan? What happens if you do not do an annual marketing plan?
What is the purpose of a marketing plan? What happens if you do not do an annual marketing plan?
Act6.1 What is the purpose of a code of conduct and what do they normally contain?...
Act6.1 What is the purpose of a code of conduct and what do they normally contain? Discuss in 120–150 words.
What is Audit? An organization do audit for what purpose in their financial statement? What are...
What is Audit? An organization do audit for what purpose in their financial statement? What are the types of audit and explain each part? (10 Markes)
What do you think is the purpose of a deductible in property insurance?
What do you think is the purpose of a deductible in property insurance? Please be specific in your response to this question and provide an example.
What are minutes of meetings and what purpose do they serve? (90–120 words)
What are minutes of meetings and what purpose do they serve? (90–120 words)
What is the purpose of Social Welfare Functions? What problem or issue do they attempt to...
What is the purpose of Social Welfare Functions? What problem or issue do they attempt to address in market economies? How do SWFs attempt to solve this? Explain the difference between the Utilitarian SWF and the Rawlsian SWF.
What is the purpose of economic sanctions? Are they a fair practice? What problems do sanctions...
What is the purpose of economic sanctions? Are they a fair practice? What problems do sanctions pose for the nation initiating the sanctions? When are sanctions most successful in achieving their goals? In your response, provide a real-world example to justify your arguments. For your example, were sanctions effective at achieving their objective?
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT