Hello_world_small issue?

[Altera_Forum]

Quartus version: 9.0sp2 

Nios EDS version: 9.0sp2  I met a problem which confuse me several days,when I code a simple led flashing program by hello_world_small temple,the console give me the state below,but led not flashing,I hav confirm the HW connection and RST pull high.But when I try the debug as hardware mode,it can be work step by step,but when I resume the program it seems running(view in disasemble),but PIO not working, anyone could help me?  Console in Run As mode: Using cable "USB-Blaster [USB-0]", device 1, instance 0x00 Pausing target processor: OK Initializing CPU cache (if present) OK  Downloading 00000000 ( 0%) Downloaded 1KB in 0.0s   Verifying 00000000 ( 0%) Verified OK  Leaving target processor paused   Console in Debug As mode: mi_cmd_stack_list_frames: No stack. No symbol "new" in current context. No symbol "IOWR_ALTERA_AVALON_PIO_DIRECTION" in current context. Single stepping until exit from function _start,  which has no line number information.

[Altera_Forum]

It is so strange,when I add one line code of "printf("Leds are ON\n");" 

It works!

[Altera_Forum]

Are you perhaps toggling the LED too fast for the human eye to see such that it looks like it is on continuously?

[Altera_Forum]

Thanks Kevin,you r right, I should hav a oscillograph now:p