PBP command execution time

[HenrikOlsson]

Robert,
1, 2 MHz aren't supported oscillator speeds. From the manual:

There are a limited number of valid numbers that can be used: 3 (3.58MHz), 4, 8, 10, 12, 16, 20, 24, 25, 32, 33, 40, 48, 64. These are the only frequencies for which PBP is able to accurately calibrate its timing.

As for the Saleae LOGIC....Your computer can't keep up due to loading on the USB bus (or too much other stuff going on). Make sure that the LOGIC it's the only device on that USB Host controller. If you don't know, just try another USB port.

But, I don't know what was wrong with me this morning. I was probably thinking in terms of instruction cycles of the PIC.....
If the samplig rate is 4MHz then the shortest resolvable time is of course 250ns and not 1us as I wrote. Even so I'd definitely try to get the sample rate up a notch (or two).

/Henrik.

[Demon]

I was fixated looking at the INCLUDE file, not the manual.

And I realized after I went to bed that I am offset by one command in my Saleae pic in the other thread. The action occurs AFTER the command, not before, d'uh.

I remove all other USB peripherals when I do my test and was able to run the pgm at 4MHz and the probe at 8MHz.

I still get the same structure, but with new timings naturally. It doesn't seem the be missing anything, and it seems neither was the previous attempt.

mainloop:
    TRISA = %11111100
    PORTA = %00000001       ' LED 1
    PORTA = %00000010       ' LED 2

    TRISA = %11110011
    PORTA = %00000100       ' LED 3
    PORTA = %00001000       ' LED 4
    goto mainloop
End

Robert

[HenrikOlsson]

Hi,
As Richard pointed out earlier, something like TRISA = %11111100 or PortA = %00000001 compiles to TWO assembly instructions:
movlw low (0FCh)
movwf TRISA
each taking one instruction cycle. If the PIC is clocked at 4MHz, one instruction cycle is 1us so TRISA = %11111100 takes two us.

The Goto MainLoop compiles to a bra instruction which takes two instructions.

Your complete program executes in 14 cycles, or 14us at 4MHz.

Then, as have also been pointed out, the compiler MAY inject a clear WDT instruction. Turn it off and tell the compiler to stop tickle the dog if you want to be sure.

/Henrik.

[Demon]

Yup, I got those values also by highlighting from one point in a pass to the same point in the next pass. I couldn't point before the top TRIS, there's no pulse break to select. That's why I used after PORT instead, I can select it at the beginning and end of a pass.