MIPS - Intro

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MIPS

- its acronym is Microprocessor without Interlocked Pipeline Stages
- reduced instruction set computer (RISC) instruction set computer (ISA) 
- it has 32-bit general purpose registers

1.0 Memory Allocation

-MIPS processor typically divided its memory by 3 parts.....
     i) text segment : hold machine language code for instructions in 
                                    the source file (user program)
    ii) data segment : holds  the data that the program operates on. 
                                   : divided with 2 parts 
           > static data : the size data that allocated is not changes 
                                     when a program access them
           > dynamic data : the data is allocated and deallocated 
                                           by the program executes
   iii) stack segment : resides at the top of user address space

2.0 Register

- 32-bit general purpose registers (0 - 31)
- $0 always has zero value
- $at ($1), $k0 ($26) and $k1 ($27) are reserved 
      > for assembler and operating system 
      > not be used by the user programs and compiler
- $a0 - $a3 ($4 - $7) used to pass 1st 4 arguments to routines
- $v0 & $v1 ($2 - $3) used to return values from functions
- $t0 - $t9 ($8 - $15, $24, $25) are caller-saved registers 
      > hold temp values 
- $s0 - $s7 ($16 - $23) called as callee-saved registers
      > hold long-lived values that should be preserved across calls function
- $gp ($28) a global pointer 
      > point to the middle of 64k block of memory in static data segment
- $sp ($29) stack pointer
      > point last location of stack
-$fp ($30) is a frame pointer
- $ra ($31) has return address written jal instruction

3.0 System Call

- how a program requests a service from an operating system's kernel  
- include :- 
      > hardware related services (e.g. accessing the hard disk)
      > creating and executing new processes 
      > communicating with integral kernel services (like scheduling)
- provide an essential interface between a process and the operating system

System call function

      

Service	System call code	Arguments	Result
print_int	1	$a0 = integer
print_float	2	$f12 = float
print_double	3	$f12 = double
print_string	4	$a0 = string
read_int	5		$v0 = integer
read_float	6		$f0 = float
read_double	7		$f0 = double
read_string	8	$a0 = buffer $a1 = length
sbrk (allocate memory)	9	$a0 = amount	$v0 = address
exit	10
print_char	11	$a0 = char
read_char	12		$v0 = char

4.0 Assembly Language 

- made up of plain text file 

- made up of 2 type statements 

     i) assembler directive

          > tell assembler how to translate a program 

          > cannot be translated into machine code 

     ii) executable instruction 

          > a program will be translated into machine code 

          > sometimes called as program code

- contain 4 columns

Column 1

Column 2

Column 3

Column 4

              

1) Column 1 : Label (Optional)

- mark specific point in a program code

2) Column 2 : Opcode (Operation Code)

- basic operation and format of an instruction

3) Column 3 : Operand 

- contain 

     i) registers 

     ii) shift amount

     iii) label to jump into 

     iv) constant

     v) address

4) Column 4 : Comment 

- have ' # ' on a line 

- MIPS simulator will skip this comment

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