ARM Assembly Language, 2nd Edition

Chapter 13

Subroutines and Stacks

13.1 Introduction

Subroutines, which are routines dedicated to focused or shorter tasks, occur in nearly all embedded code, often to perform initialization routines or to handle algorithms that require handcrafted assembly. You’re very likely to write subroutines when you come across a large problem to solve. The notion of divide-and-conquer aptly applies to writing assembly code—it’s just easier to get your head around a problem by describing it as a sequence of events, worrying about the low-level details when you write the event itself. For example, you could break a large program that controls a motor into something that looks like

main	BL	ConfigurePWM

	BL	GetPosition

	BL	CalcOffset

	BL	MoveMotor

	...