ECE382_Lab01

MSP430 Calculator

#####Purpose Create a calculator program in assembly that reads a string of specific bytes as a math function and solves it The following bytes represent operations 0x11 - add 0x22 - subtract 0x33 - multiply 0x44 - clear 0x55 - end

##Pre-Lab The program will take a mathmatical operation as an input in the form of an array of bytes. The array will need a pointer which will be a register the array pointer will need to change after each operation is done and increment by enough to point at the next operation there will need to be temp variables to store operands. A register will do this.

#####Psuedo Code

final ADD_OP = 0x11;
final SUB_OP = 0x22;
final MUL_OP = 0x33;
final CLR_OP = 0x44;
final END_OP = 0x55;

input[arrayPtr] = a bunch of operations;

result[] = 0x230-0x240;

main(){
operand = input[arrayPtr];
operation = input[arrayPtr+1];
2ndOperand = input[arrayPtr+2];
  if(operation == 0x11){
    add();
  }else if(operation == 0x22){
    sub();
  }else if(operation == 0x33){
    mul();
  }else if(operation == 0x44){
    clr();
  }else if(operation == 0x55){
    end();
  }
}
add(){
  result[] = operand + 2ndOperand;
  arrayPtr = arrayPtr+3;
  jmp main;
}
sub(){
  result[] = operand - 2ndOperand;
  arrayPtr = arrayPtr+3;
  jmp main;
}
mul(){
  result[] = operand * 2ndOperand;
  arrayPtr = arrayPtr+3;
  jmp main;
}
clr(){
    result[] = 0x00;
    jmp main;
}

##Lab Process The lab design process was broken into 2 main parts, the switch "if else" statements and the actual mathmatical operation functions. First the switches were made. ######Case Switch

  	cmp.b	#0x11, r6
	jeq	ADD_OP
	cmp.b	#0x22, r6
	jeq	SUB_OP
	cmp.b	#0x33, r6
	jeq	MUL_OP
	cmp.b	#0x44, r6
	jeq	CLR_OP
	cmp.b	#0x55, r6
	jeq	END_OP
	jmp	END_OP

Next the operations were dealt with ######Add The add operation was simple, add the two registers and return, oveflow was also considered

add.b	r7, r8
jc	AddOverflow
jmp	reset

######Subtract The subtration operation was similar to the addition, overflow had to be handled differently

sub.b	r7, r8
cmp	#0xFF, r8
jeq	SubOverflow
jmp	reset

######Multiply Multiplying in assembly was accomplished used a methid know as peseant multiplication where one

MUL_OP		
		mov.w	r7, r13
		mov.w	#0x00, r9
		rra.b	r13
		jc	MulAdd
MUL_LOOP	
		cmp.b	#0x01, r7
		jeq	reset
		rla.b	r8
		jc	AddOverflow
		rra.b	r7
		jnc	MUL_LOOP
MulAdd		
		rla.b	r8
		add.b	r9, r8
		jc	AddOverflow
		jmp	MUL_LOOP

difficulties with the multiplication method occured becasue I initilly didn't have the subtraction overflow properly handled. ######B Functionality To check for overflows the jc instruction was used. If there was a carry, an overflow occured

#####Difficulties/Debugging The hardest part of the program was getting the pointer to always line up with the right place in the "input array" the "pointer" in the program was a register that incremented after each reference.