STM32L052使用ST_LINK仿真,突然不能使用,出现下面的错误,求解决,非常感谢!

Fri Oct 21, 2016 17:50:21: IAR Embedded Workbench 7.70.1 (armproc.dll)
Fri Oct 21, 2016 17:50:21: Loaded macro file: D:\Program Files\IAR Systems\Embedded Workbench 7.5\arm\config\debugger\ST\STM32L0xx.dmac
Fri Oct 21, 2016 17:50:21: Loaded macro file: D:\Program Files\IAR Systems\Embedded Workbench 7.5\arm\config\flashloader\ST\FlashSTM32L0xx.mac
Fri Oct 21, 2016 17:51:29: Fatal error: ST-Link, No MCU device found   Session aborted!
Fri Oct 21, 2016 17:51:29: Unloaded macro file: D:\Program Files\IAR Systems\Embedded Workbench 7.5\arm\config\flashloader\ST\FlashSTM32L0xx.mac
Fri Oct 21, 2016 17:51:29: IAR Embedded Workbench 7.70.1 (armproc.dll)

IAR工具版本为IAR7.10
我的工程设置如下:
general option-->target-->device:ST STM32L052C8

debugger-->setup-->driver:ST-LINK

ST-LINK-->setup-->interface:SWD

换个stlink或者jlink试试