Accurate Delay Function

Other Parts Discussed in Thread: TMS570LS3137, HALCOGEN

Short explanation

I am using a TMS570LS3137 and I require an accurate delay of 500ns or longer. I am unable to do so with both the RTI Timer. The fastest delay I could get from the RTI  (without the pin toggling overhead of 455.5ns) was 700ns (32 RTI1CLKS, 129 CPU clocks). Is this correct? I can't find any documentation on the overhead of the RTI timer or the fastest it can run.

Is there a better, faster, more precise way to go about this?

Long explanation

I have been using Halcogen to help generate our code for us so I will start there. Using the rtiBlinky example, I modify it by setting the clocks to 16Mhz CLK input, PLL 180MHz, Counter0clk 90MHz, and RTI1CLK to 45MHz.

I change which pin is my output

ioSetDirection(mibspiPORT3, 0x00000200);

For my first test comment out everything and just sit in the while(1) and toggle that pin to measure my real world toggle time offset (time that the pin is set high) with the code below.

gioSetPort(mibspiPORT3, gioGetPort(mibspiPORT3) ^ 0x00000200);

Pin toggling overhead = 455.5ns

I then move the toggle function to the rtiNotification function and I added a line to change the period before I start the counter.

rtiSetPeriod(rtiCOMPARE0, 1000);

I then went through and swept through a bunch of different periods (RTI1CLKs between the interrupt firing) I call them ticks in the table below

As you can see there is a definite cieling i am hitting but i can not find it being discussed in any of the documentation. Is there a better faster way to go about making a precise delay function of 500ns?

rtiSetPeriod(rtiCOMPARE0, 1000);