GenericSecureUartHost.exe用小程序进行UART2串口解锁JTAG时，出现(Serial Port): Read error: 操作已超时，请问是什么情况

(File IO): Read 62512 bytes from file F:C674x_OMAPL1x_Generic_Security_Flash_Boot_UtilsOMAP-L138_Secure_FlashAndBootUtils_trunkOMAP-L138_SecureGNUAISUtilsBootSample.bin.
(Serial Port): Opening COM16 at 115200 baud...
(AIS Parse): Read magic word 0x41504954.
(AIS Parse): Waiting for BOOTME... (power on or reset target now)
(AIS Parse): BOOTME received!
(AIS Parse): Performing Start-Word Sync...
(Serial Port): Read error: 操作已超时。
(AIS Parse): I/O Error in read!
(AIS Parse): Boot aborted.
(Serial Port): Closing COM16.
波特率是115200，UART2串口
1、为啥刚收到BOOTME received!再往下就不行了呢？
2、这个解锁的小程序有啥要求么？