Check two registers for equal/not equal on DLX program

DLX provides two instructions for comparing numbers:

1. seq (set if equal)
2. sne (set if not equal).

Seq instruction example:

Seq result register,compare1 register,compare2 register
Result register will be 1 if the registers are equal otherwise 0

Use branch true (bt) or branch false (bf) to compare result register

1:  seq r1,r2,r4 ;Checks if r2=r4  
2:  bt r1,L1 ; if true (Branch true ) Jump to L1  
3:  <OtherStatements> ;If false execute this  
4:  jr r31 ;end program  
5:  L1 ;Jump to here if condition fails  
6:  jr r31 ;end program  

Sne instruction example: 
Sne result register,compare1 register,compare2 register
Result register will be 1 if the registers are not equal otherwise 0
Use branch true (bt) or branch false (bf) to compare result register

1:  sne r1,r2,r4 ;Checks if r2=!r4  
2:  bt r1,L1 ; if true (Branch true ) Jump to L1  
3:  <OtherStatements> ;If false execute this  
4:  jr r31 ;end program  
5:  L1 ;Jump to here if condition fails  
6:  jr r31 ;end program  

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Halt Instruction on DLX Program

Halt is a command is equal to Stop or pause .

Once executed ,DLX program need to re run again 

Formal Description:
When this instruction is executed, the processor ceases fetching and executing instructions. A halted processor can only be restarted by some means external to the processor, such as a reset button.

Example code.

 halt  

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Jump to Subroutine & Jump Return instruction on DLX Program

Jump to Subroutine & Jump Return instruction on DLX Program

Example code

Jal subroutine name

Sub routine

Jr r31 to return to main program

Example Jump to Subroutine & Jump Return instruction on DLX Program 

  .start main ;Start program and jump to label main  
 main:       
 jal calculator;jump and link to calculator  
 halt ; halt program after executing calculator sub routine  

 calculator: ;calculator sub routine  
 add r1,r2,r3  
 jr r31 ;back to main method and execute halt statement  

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Unconditional Jump on DLX Program

Jump Instruction used for skipping some portion of sequential program

Jump instruction can be used conditional statements like IF,While,For

Example Jump DLX code 1

 j End;Jump to label End  
 add r1,r2,r3  ;Skip this command  
 End  ;label end  
 jr r31  

Example Jump DLX code 2

 add r1,r1,r2  
 j end;Jump to end label  
 sub r1,r0,r1 ;Never gets here...  
 subi r2,r2,2  
 end addi r1,r1,1  

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Subtract two Values in DLX Programming

Subtraction commands on DLX

1:  sub r1,r2,r3   ;Subtract Signed integers  
2:  subi r1,r2,100 ;Subtract Signed integers Immediate  
3:  subur1,r2,r3   ;Subtract Unsigned integers  
4:  subui r1,r2,100;Subtract Unsigned integers Immediate  

Explanation of code for subtracting from 2 registers

1:  ; #r1 register=0  
2:  ; #r2 register=10  
3:  ; #r3 register=30  
4:  ; Before execution  
5:  sub r1,r2,r3  
6:  ; After execution  
7:  ; #r1 register=20  
8:  ; #r2 register=10  
9:  ; #r3 register=30  

Explanation of code for subtracting register from immediate value

1:  ; #r1 register=0  
2:  ; #r2 register=10  
3:  ; Before execution  
4:  subi r1,r2,30  
5:  ; After execution  
6:  ; #r1 register=20  
7:  ; #r2 register=10  

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Adding two Integer values in DLX

Adding two Integers from two Registers Example code:

1:  Add r1,r2,r3 ;r1=r2+r3  

Explanation of code:

1:  #r1 register=0  
2:  #r2 register=1  
3:  #r3 register=2  
4:  //before execution  
5:  Add r1,r2,r3 ;r1=r2+r3  
6:  //after execution  
7:  #r1 register=3  
8:  #r2 register=1  
9:  #r3 register=2  

Adding a register with immediate value Example code

1:  addi r1,r2,100  

Explanation of code

1:  #r1 register=0  
2:  #r2 register=1  
3:  //before execution  
4:  addi r1,r2,100  
5:  //after execution  
6:  #r1 register=101  
7:  #r2 register=1  

Addition Commands on DLX

1:  add r1,r2,r3   ;Adding Signed integers  
2:  addi r1,r2,100 ;Adding Signed integers Immediate  
3:  addu r1,r2,r3   ;Adding Unsigned integers  
4:  addui r1,r2,100 ;Adding Unsigned integers Immediate  

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Loading and Storing Value to DLX Ram from Registes

DLX Code

1:  lw r5,16#100  
2:  sw 16#200,r5  

Explanation DLX Code

1:  # Ram 100=0  
2:  r5 register=8  
3:  sw 16#100,r5 //Copy r5 resgiter value to memory 100  
4:  r5 register=8  
5:  # Ram 100=8  
6:  lw r5,16#100 //Copy memory into r5 register  
7:  # Ram 100=8  
8:  r5 register=8  

Tags:Loading Storing DLX registers, Backup DLX Registers,Copy ram to Register on DLX

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