Controlling a datapath

contents: 0-1. CA Intro

Controlling a datapath

main control

Control signals are derived from given instructions

• rs is always being read

• rt is being read except when the instruction is lw.

    - It is for loading

ALU control

• Load / store instructions: add

• Branch instructions: subtract

• R-format instructions: depends on a function field in the instructions

• Main Control Unit determines the ALUOp value

• Whatever the funct codes are, if the opcode is lw, sw, or beq, ALU fuction is determined automatically