System Workbench for STM32

Thank you! Now I can see printf works, but.....

When I "Run" the code, the discovery board just die as there is no error information.
When I "Debug" the code, it can run well for a while and I can see the printf information. However, I will see the following information after a while...

No source available for "_swiwrite() at 0x8000516"

Semihosting is on.
Error: jtag status contains invalid mode value - communication failure
Warn : target STM32F469.cpu is not halted
Polling target STM32F469.cpu failed, trying to reexamine
Examination failed, GDB will be halted. Polling again in 100ms
Info : Previous state query failed, trying to reconnect
Polling target STM32F469.cpu failed, trying to reexamine
Info : STM32F469.cpu: hardware has 6 breakpoints, 4 watchpoints

Any comments will be appreciated.