Table of Contents
When trap flag is set then?
If trap flag is set (1), the CPU automatically generates an internal interrupt after each instruction, allowing a program to be inspected as it executes instruction by instruction. If trap flag is reset (0), no function is performed.
What is the use of trap flag in 8086?
Trap Flag (T) in 8086 is used for on-chip debugging. Setting the trap flag puts the microprocessor into a single step mode for debugging. In single stepping, the microprocessor executes an instruction and enters into a single step ISR.
Which flag is used for single stepping of instructions?
Trap Flag
Here I searched that: Trap Flag (T) – This flag is used for on-chip debugging. Setting trap flag puts the microprocessor into single step mode for debugging. In single stepping, the microprocessor executes a instruction and enters into single step ISR.
Which instruction removes flag register from stack?
In a system using x86 architecture, the instructions CLI (Clear Interrupt) and STI (Set Interrupt). The POPF (Pop Flags) removes a word from the stack into the FLAGS register, which may result in the Interrupt flag being set or cleared based on the bit in the FLAGS register from the top of the stack.
How do you clear a trap flag?
To reset the trap flag, simply replace the OR instruction in the preceding sequence with the instruction: AND WORD PTR[BP+0],0FEFFH. The trap flag is reset when the 8086 does a type-1 interrupt, so the single-step mode will be disabled during the interrupt-service procedure.
What are flag manipulation instructions?
Flag Manipulation and Processor Control Instructions
| Instruction | Description |
|---|---|
| CLC | Clear Carry Flag: This instruction resets the carry flag CF to 0. |
| CLD | Clear Direction Flag: This instruction resets the direction flag DF to 0. |
| CLI | Clear Interrupt Flag: This instruction resets the interrupt flag IF to 0. |
What is use of trap flag Mcq?
A trap flag permits operation of a processor in single-step mode. If such a flag is available, debuggers can use it to step through the execution of a computer program.
What is single step mode?
When a system is instructed to single-step, it will execute one instruction and then stop. The contents of registers and memory locations can be examined; if they are correct, the system can be told to go on and execute the next instruction.
How do you set or clear interrupt flag?
Clear Interrupt Flag (cli)
- Operation. 0 -> IF.
- Description. Clears the interrupt flag if the current privilege level is at least as privileged as IOPL; affects no other flags.
- Example. Clear the interrupt flag: cli.
What is single-step mode?
What are flag manipulation instructions give examples?
What are flag manipulation instructions give examples? Instructions to transfer flag registers LAHF − Used to load AH with the low byte of the flag register. SAHF − Used to store AH register to low byte of the flag register. PUSHF − Used to copy the flag register at the top of the stack.
What are string instructions?
The string instructions operate on strings of bytes. Operations include storing strings in memory, loading strings from memory, comparing strings, and scanning strings for substrings.