Chapter 5. Instruction Set

Background of ARM and Thumb Instruction Set

The early ARM processors use a 32-bit instruction set called the ARM instructions. The 32-bit ARM instruction set is powerful and provides good performance, but at the same time it often requires larger program memory when compared to 8-bit and 16-bit processors. This was and still is an issue, as memory is expensive and could consume a considerable amount of power.
In 1995, ARM introduced the ARM7TDMI processor, adding a new 16-bit instruction set called the Thumb instruction set. The ARM7TDMI supports both ARM instructions and Thumb instructions, and a state-switching mechanism is used to allow the processor to decide which instruction decode scheme should be used (Figure 5.1 ...

Get The Definitive Guide to the ARM Cortex-M0 now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.