... Extension.In architecture versions prior to version 5, and in non-E variants of architecture version 5 and above, bit[27] of the CPSR and SPSRs should be treated as described in Other bits on page ... (SBZ) on ARM architecture version 3 and below, and on non-T variants of ARM architecture version 4. No instructions exist in these architectures that can switch between ARM and Thumb states. On ... MSR instruction, as part of its function of writing a new value to the CPSR or SPSR.• Execution of MRC instructions with destination register R15. The purpose of such instructions is to transfer...