ECE 120 Lecture Notes - Lecture 30: Subroutine, Schenkerian Analysis, Infinite Loop

• School: University of Illinois
• Department: Electrical and Computer Engineering
• Course: ECE 120
• Professor: Kindratenko Volodymyr

Document Summary

Control instructions change the sequence of the instructions that are executed. They achieve this by directly manipulating the value of pc register. Jmp - unconditional jump: br conditional branch, trap invokes an os service call, ret return from subroutine will introduce in ece 220, rti return from interrupt will introduce in ece 220. Jsr/jsrr subroutine call will introduce in ece 220. For now we will study only jmp, br, and trap instructions. Operation: load the pc with the contents of the register specified by bits 6-8: pc baser. Datapath relevant to the execution of this instruction: example: 1100 000 111 000000; jmp r7. Jmp instruction has no limitations on where the next instruction to be executed is located since the full 16-bit memory address can be stored in the register. Operation: if any of the condition codes tested is set, increment the pc with the sign-extended. In other words, branch is taken if specified condition is true.