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PythonExtra/docs/reference/asm_thumb2_mov.rst
Damien George ea8be373a9 py/inlinethumb: Remove 30-bit restriction on movwt instruction. 
movwt can now move a full 32-bit constant into a register.
2016-01-07 16:34:11 +00:00

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Register move instructions

Document conventions

Notation: Rd, Rn denote ARM registers R0-R15. immN denotes an immediate value having a width of N bits. These instructions affect the condition flags.

Register moves

Where immediate values are used, these are zero-extended to 32 bits. Thus mov(R0, 0xff) will set R0 to 255.

  • mov(Rd, imm8) Rd = imm8
  • mov(Rd, Rn) Rd = Rn
  • movw(Rd, imm16) Rd = imm16
  • movt(Rd, imm16) Rd = (Rd & 0xffff) | (imm16 << 16)

movt writes an immediate value to the top halfword of the destination register. It does not affect the contents of the bottom halfword.

  • movwt(Rd, imm32) Rd = imm32

movwt is a pseudo-instruction: the MicroPython assembler emits a movw followed by a movt to move a 32-bit value into Rd.