ARM Assembly Language, 2nd Edition

Chapter 17

ARM, Thumb and Thumb-2 Instructions

17.1 Introduction

Throughout the book, we’ve been using two different instruction sets, ARM and Thumb-2, only mentioning 16-bit Thumb here and there. Recall that the Cortex-M4 executes only Thumb-2 instructions, while the ARM7TDMI executes ARM and 16-bit Thumb instructions. Keeping in mind that a processor’s microarchitecture and a processor’s instruction set are two different things, Table 17.1 shows how the ARM processor architectures have evolved over the years, along with the instruction sets. They often get developed at the same time, but it is possible for a given microarchitecture to be modified only slightly to support additional instructions, adding more control logic and a bit more datapath, ...