http://e2e.ti.com/support/low_power_rf/f/851/t/167527.aspx

Please disconnect then reconnect the USB cable and try again. If that doesn't work, one of two things might help:
把仿真器重新连接
1) Uninstalling the port . Right click on it in device manager and click uninstall. Don't uninstall the drivers, then disconnect and reconnect the USB cable. The port should reinstall and you can try the Download shortcut again

2) Reassigning the com port - Right click on the COM port in Device manager, click properties, then go to Port Settings -> advanced and select a new port number. Even though it might complain that it is being used, if it doesn't actually show up in device manager as used you can use it. Press ok to reassign it and then disconnect then reconnect the USB cable.
把串口的端口号删除，重新安装驱动或者重新分配端口号