The MIPS ISA is a simple instruction set that is broken up into three distinct types of instructions, all 32-bits in length:
- R-Type or Register MIPS instructions are used for most arithmetic and logic operations
- I-Type or Immediate instructions are used primarily for data transfer and immediate operations using constants
- J-Type or Jump instructions are used to jump the program to the specific instruction, such as in a loop
Along with the instruction types, it also details that each CPU will have 32 registers, each capable of holding a 32-bit piece of data. MIPS operates on data that is stored in the register or with a 16 bit ‘immediate’ piece of data. Immediate data is typically a constant that can be sent to the processor so it doesn’t need to take up space in a register.
MIPS is often used in distributed/embedded technologies because of its RISC architecture and concise instruction set. Some advantages to this in a small system include limited space requirements, increased battery life, and little to no customer interaction.
Instruction Format
Here is a sample R-type instruction:
All R-type instructions use this instruction format according to the MIPS documentation. This example introduces several abbreviations above in the machine code/instructions. They will be used throughout the rest of this lesson, so let’s define them now:
| Abbreviation | Definition |
|---|---|
op |
OPCODE |
rs |
first source register |
rt |
second source register |
rd |
destination register |
shamt |
bit shift amount |
func |
extra bits for additional functions |
Instructions
Create a new variable, answer1, and set it equal to the answer of:
- How many bits long is a MIPS instruction?
Create another variable, answer2, and set it equal to the answer of:
- How many types of instructions are there in MIPS?
Finally, create another variable, answer3, and set it equal to the answer of:
- What is the abbreviation used for the destination register?