Why my Nios II run slowly ?

Dear all,

I have do experiment on the Cyclone V SOC. [Helio evaluation board]

And I put one nios/e and onchip-ram into the FPGA fabric.

Currently, I could read/write the data in/out from Onchip RAM.

Now, I am measuring the time duration for my source code.

I discover that each instruction runs slowly.

Below is my simple source code.

I don't understand that the one line[*pdata = i++;] I comment , it needs to take 1us.

It should not be correct performance.

Or should I choose the better version of Nios II ?

Anyone could suggest or hint me why and what to do?

Attached file is my zip file of QSYS.

# include <stdio.h># include "system.h"# include "altera_avalon_pio_regs.h"

unsigned int LED_TOGGLE = 0;

unsigned char *pData = ONCHIP_MEMORY2_1_BASE;

int main()

{

int i = 0;

printf("Hello from Nios II!\n");

while(1)

{

IOWR_ALTERA_AVALON_PIO_DATA(LED_PIO_BASE,LED_TOGGLE);

LED_TOGGLE = ~LED_TOGGLE;

//*pdata = i++;

}

return 0;

}