Lab Assignment- Using Subroutines and Macros
Overview
The purpose of this lab is to program the MC8051 to add multi bytes two signed integers.. To simplify our laboratory, we will assume three bytes long (24 bits) signed integers. Each of the three bytes will be defined in three consecutive code memory bytes using the "DB" assembler directive. The program will store the answer in three consecutive data memory bytes starting at Ram address 40H. The program will also display the answer on P0, P1, and P2 staring with the LS Byte in P0. Port 3 pin 0 (P3.0) will be set if an overflow takes place, otherwise it will stay cleared. Three versions of the program will be implemented starting with all code included in one main program. The second implementation will employ two subroutines to make advantage of the repeated code blocks. The final implementation will utilize two Macros to reduce the size of the source program and improve its readability.
Steps
1. First, configure your code and data memory. The "MAIN:" program starts at code memory location 30H. The first integer uses code memory locations 100H, 101H, and 102H in the Intel MC8051 little endian format. The second integer uses code memory locations 105H, 106H, and 107H.
2. Second, configure parallel port 0, port 1, port 2, and P3.0 for output. Write and debug the code to add the two integers and store the answer in data memory locations 40H, 41H, and 42H. Update P0, P1, and P2 to display the same addition result. Flag an overflow condition on P3.1 by setting it.
3. Third, rewrite the program utilizing subroutines to make use of the repeated code blocks. Define the created. Subroutines after the main program before the program "END" directive.
4. Fourth, rewrite the program utilizing Macros to make use of the repeated code blocks. Define the created. Macros before the main program code. Unlike labels, the assembler will issue an error if Macros are not defined before they get referenced. Every Macro must end with "EMAC" directive. The Macro starts by its name followed by the word "MACRO". Example of a "SUM" Macro is the following:
SUM MACRO
------- -----------
------- -----------
EMAC
Type the name of the Macro at desired locations in your assembly source program as needed for the assembler to insert the Macro object code in the final object file.
5. Fifth, check the three programs for different integers and verify the overall operations. Make sure to test cases producing an overflow. Also make use of break points in the Keil debugger to enhance and speed up the checkout.
6. Document and submit your final report along with the well documented list file. Also describe the steps and tools used in debugging your program.
7. Describe how to modify / redesign your program to perform the addition of two multi bytes integers up to 16 bytes long; one stored at code memory starting address of 100H and the other at 110H. The length of the two integers is input from port 3 (P3). The answer is stored at data memory starting at address 40H through 4FH.