Simple asm delay ?

[ultiblade]

Dear Jerson & Bruce,

I could not get here earlier, sorry. I appreciate your efforts !

Jerson, if i declare the delay variable as a byte, it takes even longer.
I just don't understand .. The delay macro i found works perfect if given a number straight from the call, if it is fed by a variable the delay jumps to 20 or 30us. It also seems that the delay is fixed after that, if i compile @ wait 1000, it delays a perfect 1000 cycles, if i compile @ wait ledred (i.e. ledred = 100) it delays 20uS no matter what ledred is ?

Bruce, your asm code also does the trick, perfect 1us or 50us delays, pretty neat. But it also suffers from the same problem. If i compile @ Delaycycles 200 if works perfect, if i compile ledred var byte, ledred = 200, @ delaycycles _ledred it gives a delay of 33uS no matter what the value of the leded var is ??

Apart from that, i need to do a delay between 1 and 1000uS, using tmr0 the max delay will be 256, and i can use the Bruce asm up to 512, the ASM code i posted earlier can go up to about 1024.

I would use the 16-bit TMR1 if it was available but i need that to do a 100Hz sync (count) interrupt...

Any ideas ?

[Bruce]

@ delaycycles _ledred it gives a delay of 33uS no matter what the value of the leded var is ??

That's because when you pass _ledred to the macro as the argument, it uses the 'address'
of ledred, and not the actual value in RAM. Look at the address PBP places ledred at to see
why that happens.

You can't put a macro inside a loop with a variable as the argument. What you're looking to do just
isn't possible (as far as I know) with a macro inside the loop, and calls to any .asm routine, timer, etc,
just aren't going to give you from 1uS to 1000uS delay periods you need immediately after
placing a value on GPIO.

I would re-think the whole process if I'm stuck at 8MHz, or switch osc speed & PIC to support using
the pauseus commands.

[ultiblade]

Hi Bruce,

Thank you for your detailed answer ! All is clear now.

I have adapted the code in a way that the led's never go below 12uS, that way the 'color' switch on and off effect (color switches on for 12uS instead of 1uS) does not occur. This makes the colors somewhat more pastel, but it is still a smooth fade and a cool effect.

And, yes, if i'm going to make a new design i will certainly use a larger external osc ..

Thanks for all your answers and information !

Best regards,
UB

[Bruce]

Grab a new 8-pin PIC12F1822 with 32MHz internal osc when they come out. Then you can
get PAUSEUS down to 2uS. These even have an onboard EUSART.

[ultiblade]

Yep, if only it had eeprom .... :-(

[Bruce]

The preliminary specs state it does. Data EEPROM (bytes) 256

[ultiblade]

You are right ! Missed that one, sorry ..

Will order some samples as soon as possible, hoping that support for the part in PBP will be available soon ..

Best regards,
UB