Lab Assignemnt: TRAPs and Subroutines - Memory Dump Computer Organization
PURPOSE
In this lab, students will gain familiarity with the use of low-level subroutines, caller/callee register saving policy, and TRAP calls.
ASSIGNMENT
Using the LC-3 simulator, you will construct an assembly-level program that prompts the user for a starting address (in hex) and an ending address (in hex). Your program will then output the contents of memory (in hex) between the provided ranges (inclusive).
Enter starting memory address:
x3000
Enter ending memory address:
x3001
Memory contents x3000 to x3001:
x3000 xF030
x3001 xF025
Example execution of the Memory Dump routine:
I/O for this routine requires that we develop a routine to enable the input of a 4-digit hex value and a routine for displaying the contents of a 16-bit registers/memory location as a 4-digit hex value. We will implement each of these routines as TRAPs.
• Input (Trap x40): A Trap routine (invoked as TRAP x40) that reads a 4-digit hex from the keyboard and returns the value in R0. This trap may call other traps. You will develop this trap routine and locate it in memory at address x4000.
• Output (Trap x41): A Trap routine (invoked as TRAP x41) that displays the contents of R0 to the display as a 4-digit hex value. This routine should output exactly 5 characters: a leading "x" and the 4 hex digits. Do not display a carriage return/line feed/end-of-line as part of the trap call. This trap may also call other traps. You will develop this trap routine and locate it in memory at address x5000.
Develop these TRAP routines and the use them to implement a program to perform memory dumps (using the i/o format provided in the example above).
Note: The representation for output characters (ASCII) is different than the standard binary representation of the value. For example, you may find it useful to note that the ASCII representation for any single-digit value is #48 greater than the number itself. Thus, the ASCII representation of the character 0 has value #48 (x30) while the ASCII representation of the character 1 has value #49 (x31).
Attachment:- Shift_r.rar