Inline assembler for Thumb2 architectures¶
This document assumes some familiarity with assembly language programming. For a detailed description of the instruction set consult the Architecture Reference Manual detailed 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 in the above ARM manual, 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.
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 case this is impossible because Python doesn’t support concepts such as indirection. The pseudocode employed in such cases is described on the relevant page.
The following sections details the subset of the ARM Thumb-2 instruction set supported by MicroPython.
- 1. Register move instructions
- 2. Load register from memory
- 3. Store register to memory
- 4. Logical & bitwise instructions
- 5. Arithmetic instructions
- 6. Comparison instructions
- 7. Branch instructions
- 8. Stack push and pop
- 9. Miscellaneous instructions
- 10. Floating point instructions
- 11. Assembler directives
These sections provide further code examples and hints on the use of the assembler.
ARM v7-M Architecture Reference Manual (Available on the ARM site after a simple registration procedure. Also available on academic sites but beware of out of date versions.)