MIPS Instruction Types

These are the assembly instruction types. Differentiated by what each collection of bits represents.

R Type

• opcode that is always $000000$
• rs is a source register
• rt is a source register
• rd is the destination register that stores the result of the operation
• shamt is the shift amount field, used only for shift operations
• funct specifies type of instruction performed (add, sub, and, etc) from MIPS Opcodes

I Type

• opcode : the opcode from MIPS Opcodes
• rs is a source register
• rt is the destination register
• immediate is a given value for various purposes. Two zeroes are always at the end of the address
  • Note that for branching, we store the offset from the current PC, so that it can fit within immediate

J Type

• opcode : the opcode from MIPS Opcodes
  • MIPS Jump
  • MIPS Jump and Link
• address : the address offset from current address to jump to. Two zeroes are always that the end of the address