Jtag or console driver problem?

I use the NEEK board to test the application code with no MMU.

printf("%s::%d %s\n", __FUNCTION__, __LINE__, buff);

Note: The buff is current time string, and run once percent 1 second.

When disconnet the JTAG with the host PC, or no nios2-terminal, the application will pause with after about 4k bytes output.

Note: I test once is 4058 bytes.

But I connect the JTAG and nios2-terminal, the application will continue to running.

The driver config:

Character device: only select "Unix98 PTY support"

Serial drivers:

Select 3:

Altera JTAG UART support

Altera JTAG UART console support

Bypass output when no connection

Unselect:

Altera UART support or Altera UART console support