Project MARIE Start code at bottom of document
1. Introduction
The objective of this project is to reinforce your understanding of computer organization, instruction set architectures, and assembly language. You will accomplish this by writing, analyzing, and debugging an assembly language program for the MARIE processor.
You must: (i) design and write an assembly language program for the MARIE processor that inputs, transforms, stores, and then outputs a sequence of characters from the set A-Z; (ii) debug and test your program by simulating it using the MARIE simulator; (iii) document your work in a short report; and (iv) submit the report file (*.pdf), assembler source file (*.mas), assembler listing file (*.lst), and assembler executable file (*.mex).
2. The MARIE Simulator
The MARIE simulator is provided as a zip file containing Java archives (*.jar) files, documentation, and example source files. Unzip the file to a directory for use. Do the following to become familiar with the MARIE simulator
3. Design Specification
You are to design, write, test, and debug a MARIE assembly language program that inputs a sequence of characters from the set A-Z (capital letters only), stores each character in memory after it is transformed by the trivial ROT13 cipher, and then, after character input completes, outputs the transformed characters.
A template source code file (Project-2_Start.mas) is provided with this assignment. Edit this file to create a program that meets the program specifications. Note that the template includes instructions to initialize some working values that your program can use. The template also defines memory locations. You may add data memory locations. The program can be designed without additional data locations, but it may be necessary to do so for your design.
For full credit, your solution must perform the functions and satisfy the requirements specified below.
a) The first instruction of the program must be placed at location (address) 0x100 (100 hexadecimal) in MARIE's memory. This is accomplished by following the program template that is provided.
b) The constant data values (One, ChA, ChZ, ChPer, Val13, Start) should not be changed by the program. The program can load from these memory locations, but should not store to them.
c) Transformed input characters must be stored in successive memory locations beginning at location 0x200 (200 hexadecimal) as indicated in the program template. The program should store all transformed input characters before any characters are output.
d) The program should always initialize the values for Ptr in the working data memory and not rely on the values for these locations that are defined in the assembly source file. This initialization is done by the provided template file.
e) The program should work for any inputs ‘A' through ‘Z' and ‘.' (a period terminates input). In the interest of keeping the program simple, the program does not need to validate inputs.
f) When transformed characters are stored and when transformed characters are output, the program must use a loop and indirect addressing to access the values in the array of words. Note that variable Ptr is initialized in the template code and should be used in the loop. You may also define a Count variable to count the number of characters, but there are also correct designs that do not require a Count variable.
g) The program should operate as follows. Input Phase:
1. A character (A-Z or ‘.') is input. MarieSim allows the user to input a single character that is read into the accumulator (AC) with an Input instruction.
2. If character ‘.' (period) is input, then the input phase ends and the output phase begins (step 5 below). (The period may be stored in memory to mark the end of the characters or the characters can be counted to determine how many transformed characters to output during the output phase.)
3. The character that is input is transformed using the trivial ROT13 cipher (see Section 5.1).
4. The transformed character is stored in the next location in the block of memory beginning at location Start. (Variable Ptr must be updated and indirect memory addressing must be used.)
Output Phase:
5. All transformed characters are output, beginning with the first character that was transformed. The ‘.' character is not to be output. (This will require a loop using variable Ptr and indirect addressing. Note that the number of characters to output will vary and the program must know when to stop the output by relying on a ‘.' or other special character in memory, counting the number of input characters during the input phase, or some other method.)
6. After all characters are output, the program halts by executing the HALT instruction.
4. Testing
Test and debug the program using the MARIE simulator (MarieSim.jar). Debug the program using the "Step" and "Breakpoint" features of the simulator. You must test your program with the following two test cases.
Test 1: Input the eight-character sequence "VIRGINIA" followed by a ‘.' to terminate the input. Note that you need to input one character at a time into MarieSim's ASCII Input area, with each character followed by pressing the "Enter" key. The ROT13 value of each character ("IVETVAVN") should be displayed after the ‘.' character is input.
Test 2: Reload the program in MarieSim, without reassembling, input the four-character sequence "GRPU" followed by a ‘.' To terminate the input. Note the output.
When you create your source file within MarieSim (using the File > Edit menu pick), use file name lastname_firstname_P2.mas, where "lastname" is your last or family name and "firstname" is your first or given name. You can assemble your source file in the editor program. The assembly process creates a listing file (lastname_firstname_P2.lst) and an executable file (lastname_firstname_P2.mex). Load the executables file into the simulator for execution.
5. Design Notes
5.1. he ROT13 Cipher
The ROT13 cipher (see http://en.wikipedia.org/wiki/ROT13) is an old, but trivial cipher that simply rotates the characters by 13 positions. For example, ‘A' is transformed to ‘N' and ‘Z' is transformed to ‘M'.
The Project-2_Start.mas source file includes a ROT13 subroutine that almost performs this transformation. You need to fix one bug in the subroutine.
/ *****
/ This is starting code for Project 2 for ECE 5484, Fall 2016
/ Remove this header and identify your project name and your name.
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ORG 100 / Start the program at location 100 hexadecimal
/ -----
/ Input characters, transform, and store in memory until '.' is input
/ -----
Load Start / Initialize character pointer to start of block
Store Ptr
/>>>>> Add code to accomplish the input and output phases. <<<<<
Input InVal
/>>>>> Here's an example of how subroutine ROT13 is called. <<<<<
/>>>>> We'll just transform 'A' in this example then halt. <<<<<
Load ChA / Put 'A' in AC
Store InVal / Store value to be transformed into InVal
Jns ROT13 / Jump to the ROT13 subroutine
/ Upon return, the transformed character is in AC
Halt
/ -----
/ Rotate-13 subroutine: Apply ROT13 to input character in location InVal and return in AC
/ -----
/>>>>> WARNING: This subroutine *almost* works. You need to fix a bug.
ROT13, HEX 0
Load InVal / Get character
Add Val13 / Add 13
Store Hold / Save it
Subt ChZ / Check if modulo adjust is needed (past 'Z')
Skipcond 800 / No adjust needed if past 'Z'
Jump NoAdj
Add ChA / Add 'A' back to difference to perform modulo
Jump Done / Result is in AC
NoAdj, Load Hold / No adjust needed, get result
Done, JumpI ROT13 / Return with result in AC
/ -----
/ Constants (the program should not write to these locations)
/ -----
ChA, HEX 0041 / Constant value 'A' for modulo adjust in subroutine
ChZ, HEX 005A / Constant value 'Z' for modulo check in subroutine
ChPe, HEX 2E / Constant period character that marks end of input
Val13, DEC 13 / Constant rotate value of 13 for subroutine
One, HEX 1 / Constant value 1
Start, HEX 200 / Constant address for start of character block
/ -----
/ Data area (these locations are for reading and writing)
/ -----
InVal, HEX 0 / Reserved for subroutine input value
Hold, HEX 0 / Reserved for temporary variable for subroutine
Ptr, HEX 0 / Reserved for character pointer