Ch9
LC-3 I/O Operations Quiz
Test your knowledge of the LC-3 architecture and its I/O operations with this engaging quiz! From TRAP commands to the System Control Block, challenge yourself and see how well you understand the core concepts.
In this quiz, you will learn about:
- The TRAP instruction and its fun
ctionalities - How the LC-3 handles I/O operations
- Key registers and their roles in program execution
In the LC-3, the user program invokes the OS to perform an I/O operation using the TRAP command.
True
False
The System Control Block or the Trap Vector Table is a set of memory locations which contain the starting addresses of the service routines.
True
False
The TRAP instruction stores the address of the instruction following the TRAP instruction in R0 before loading the PC with the starting address of the service routine.
True
False
The instruction TRAP x23 branches off to an address stored in memory location x2300.
True
False
In the LC-3, the clock is stopped by invoking the HALT subroutine via the TRAP instruction.
True
False
The TRAP instruction performs exactly the same function as the JSR instruction.
True
False
In the LC-3, when a key on the keyboard is pressed, KBDR holds the 2's complement representation of that key.
True
False
The instruction TRAP x25 causes the PC to be loaded with the memory address:
x0025
X2500
the contents of x0025
X0250
The instruction TRAP x23 at location x4232, causes R7 to be loaded with:
X4232
X4233
contents of x4232
contents of x4233
In the LC-3, the clock is stopped by:
the STOP instruction
the instruction TRAP x25
the instruction TRAP x23
the END instruction
Which instruction in the LC-3 restarts the clock?
TRAP x30
RESTART
CLK_ST
No instruction can restart the clock.
What is wrong with the code fragment: .ORIG x3000 AND R0,R0, #0 AND R2,R2, #0 ADD R2,R2, #7 JSR SUB ADD R2,R2, ASCII ADD R0,R2,#0 TRAP x21 SUB ADD R2,R2,#9 ADD R7,R7,#1 RET ASCII .FILL x0030 .END
Nothing is wrong, the program outputs 16
We are modifying the contents of register R7. This destroys the linkage back to the calling program.
We are adding the x0030 (ascii code for 0), which is unnecessary.
TRAP x21 will not work after a subroutine call.
On execution of this program, the user inputs two numbers. Why do we need to add the value ASCII (xFFD0) to the numbers before adding them?
To strip off the ascii template, we need to add xFFD0 which is the negative of x0030 (ascii code for 0)
The program is wrong. It does not add correctly
To convert from hexadecimal to binary
The numbers are in 2's complement form
In the KBSR, an interrupt signal is generated by the AND of:
the start and stop bits
the ready bit and the interrupt-enable bit
the ready bit and the start bit
the start bit and the interrupt-enable bit
In the LC-3, the decision to opt for polling or interrupt driven I/O is made by the:
I/O device
Processor
Both of them
None of them
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