单片机MC9S12DP512下载错误—non volative memory control（奖10个积分）

10我的单片机突然下载程序报错：ERROR while loading diagnostics algorithm to target system.the chip may be secured, or the derivative seleceted may be wrong. 请问是什么原因造成的，我的单片机开始下载程序正常的，我还调试了很久的，突然发现上诉问题的，从新解锁也会出现解锁不成功的现象。derivative could not be unsecured!the unsecure cammand file might be missing or disabled. make sure the commad file defined in the unsecure panel of the command file dialog contains the correct commands to unsecure the current connected derivative and the board oscillator frequency.