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微机系统受干扰后,经常发生指令指针PC出错指向错误地址,程序便转向这错误地址继续执行,造成程序失控。指令指针出错后指向的地址是随机的,即指向CPU可寻址空间的任何单元。对于大量应用微机系统,程序区只占CPU可寻址空间的很少一部分,这样PC出错指向程序区以外的可能性就很大。如果我们能够及时发现PC指针指向程序区以外,就可以防止大量的程序失控。要判断PC指针是否出了程序区,只要在微机CPU的取指令周期判断地址线即可,这在硬件上是非常容易做到的。
After the interference of the computer system, the PC pointer of the instruction pointer PC often points to the wrong address, and the program turns to the wrong address and continues to execute, causing the program out of control. The address pointed to by the instruction pointer error is random, that is, any cell that points to the CPU’s addressable space. For a large number of applications computer system, the program area only occupy a small part of the CPU addressable space, so PC error pointing outside the program area is very likely. If we can find out in time PC pointer outside the program area, you can prevent a large number of programs out of control. To determine whether the PC pointer out of the program area, as long as the computer CPU instruction fetch cycle to determine the address line, which is very easy to do in the hardware.