TMS320F28034: question about GPIO toggle speed and asm("NOP") delay time

Part Number: TMS320F28034

Hi Team,

There is an issue from the customer need your help:

F28034, driver IO control WS2812B chip. The crystal oscillator uses internal INTOSC1 to multiply to 50M, adding an asm ("NOP"); statement, about 300ns increase the time, in theory, is not the 50ns corresponding to the 20M clock?

The first high time in the picture executes two asm ("NOP"); , the second high time performed three asm ("NOP");. The GPAQSEL1 register is configured as asynchronous. I want to know asm("NOP"); Why is latency not clock cycles, or is there another more precise delay method.

It's strange that I cannot attach my picture in this post.

void WS2812B_tx(void)
{
    Uint16 ws2812hl[24],rgb,i;

    rgb = WS2812.GRB;
    for(i=0;i<24;i++)
    {
        if((rgb & 0x00800000) == 0x800000)
            ws2812hl[i] = 1;
        else
            ws2812hl[i] = 0;
        rgb = rgb << 1;
    }
    if(ws2812hl[0])
    {
         ws2812b_H;
         asm(" NOP");asm(" NOP");asm(" NOP");
         ws2812b_L;
         //asm(" NOP");
    }
    else
    {
        ws2812b_H;
        asm(" NOP");asm(" NOP");
        ws2812b_L;
        //asm(" NOP");
   }

    if(ws2812hl[1])
    {
         ws2812b_H;
         asm(" NOP");asm(" NOP");asm(" NOP");
         ws2812b_L;
         //asm(" NOP");
    }
    else
    {
        ws2812b_H;
        asm(" NOP");asm(" NOP");
        ws2812b_L;
        //asm(" NOP");
   }

Could you help check this case?

Thanks & Regards,

Ben