3. Store registers in memory

3.1. File Specification

Symbol: Except for special notes， Rt, Rn means ARM registers R0-R7. immN means an instant value with N-bit width, so the range of imm5 is limited to 0-31. [Rn + imm5] is the content of the memory address obtained by adding Rn and offset value imm5 . The unit of offset value is byte. These instructions will not affect the condition flags.

3.2. Register storage

• str(Rt, [Rn, imm7]) [Rn + imm7] = Rt Store a 32-bit word
• strb(Rt, [Rn, imm5]) [Rn + imm5] = Rt Store one byte (b0-b7)
• strh(Rt, [Rn, imm6]) [Rn + imm6] = Rt Store a 16-bit halfword (b0-b15)

Specify the unit of immediate deviation value in bytes. So in case of str , the 7-bit value makes it possible to access the 32-bit word alignment value with the maximum deviation of 31 words. In the case of strh , the 6-bit value makes it possible to access the 16-bit halfword alignment value with the maximum deviation of 31 halfwords.