2. Load registers from memory

2.1. File Specification

Symbol: Except for special notes, Rt, Rn means ARM registers R0-R7. immN means instant value with width N, so the range of imm5 is limited to 0-31. [Rn + immN] is passed Add the content of the memory address obtained by Rn and the error immN . Error unit is byte. These instructions affect the condition flags.

2.2. Register loading

• ldr(Rt, [Rn, imm7]) Rt = [Rn + imm7] Load a 32-bit word
• ldrb(Rt, [Rn, imm5]) Rt = [Rn + imm5] Load a byte
• ldrh(Rt, [Rn, imm6]) Rt = [Rn + imm6] Load a 16-bit halfword

When a byte or a halfword is loaded, it changes from zero padding to 32 bits.

Specify the immediate error unit as bytes. Therefore, in the case of ldr , the 7-bit value makes it possible to access the 32-bit word alignment value with the maximum offset of 31 words. In the case of ldrh , the 6-bit value makes it possible to access the 16-bit halfword alignment value with the maximum offset value of 31 halfwords.