1. Register move instructions

1.1. 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.

1.2. 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, imm30) Rd = imm30

movwt is a pseudo-instruction: the MicroPython assembler emits a movw and a movt to move a zero extended 30 bit value into Rd. Where the full 32 bits are required a workround is to use the movw and movt operations.