ARM A32 NOP 4 0x00000000 This stands for andeq r0, r0, r0. The assembly instruction nop will most likely expand to mov r0, r0 which is encoded 0xE1A00000 (little-endian architecture).[3]
ARM T32 (16 bit) NOP 2 0xb000 Opcode for ADD SP, #0 - Add zero to the stack pointer (No operation). The assembly instruction nop will most likely expand to mov r8, r8 which is encoded 0x46C0.[4]
https://en.wikipedia.org/wiki/NOP_(code) тут еще интересные варианты.