Inline assembler for Thumb2 architectures

This document assumes some familiarity with assembly language programming. For a concise description of the instruction set consult the ARM Thumb-2 Instruction Set Quick Reference Card under References below. The inline assembler supports a subset of the ARM Thumb-2 instruction set described here. The syntax tries to be as close as possible to that defined by ARM, converted to Python function calls.

Instructions operate on 32 bit signed integer data except where stated otherwise. Most supported instructions operate on registers R0-R7 only: where R8-R15 are supported this is stated. Registers R8-R12 must be restored to their initial value before return from a function. Registers R13-R15 constitute the Link Register, Stack Pointer and Program Counter respectively.

Document conventions

Where possible the behaviour of each instruction is described in Python, for example

  • add(Rd, Rn, Rm) Rd = Rn + Rm

This enables the effect of instructions to be demonstrated in Python. In certain cases this is impossible because Python doesn’t support concepts such as indirection. The pseudocode employed in such cases is described on the relevant page.

Instruction categories

The following sections detail the subset of the ARM Thumb-2 instruction set supported by MicroPython.

Usage examples

These sections provide further code examples and hints on the use of the assembler.

References