Delay loop generator

Avra

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Delay loop generator

· Posted: 03.01.2008 - 09:42 · #1

Handy ASM delay loop generator can be found at http://www.avrprojects.net/articles.php?lng=en&pg=67

EDIT: New link here: http://www.home.unix-ag.org/tjabo/avr/AVRdelayloop.html

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Merlin

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Re: Delay loop generator

· Posted: 03.01.2008 - 10:25 · #2

There are a few gotchas here.

R17 and R18 are an unexpected choice. R17 is _ACCA, but _ACCB (the obvious partner) is R16.

R17 in particular is well used so you need to PUSH and POP both registers which takes up a number of cycles (2 each - a total of 8 cycles).

Obviously you need to disable and enable interrupts, which might need to be taken into account.

Finally, in AVRCo assembler, the labels must be on separate lines.

Regards

Merlin.

Avra

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Re: Delay loop generator

· Posted: 03.01.2008 - 11:17 · #3

I am aware of needed changes (it is designed for AVR Studio, not for AvrCo), but it is interesting anyway for some special applications. Registers are chosen from a drop list so we can choose ones which are more friendly with AvrCo and avoid PUSH/POP. I don't need this delay very often so it would not pay off to make this small application that generates real AvrCo code by my self, so I can live with it's faults that can be hand corrected.

Merlin

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Re: Delay loop generator

· Posted: 03.01.2008 - 11:27 · #4

Ah I see.

I missed the fact that it is an application that generates the code - even though it is obvious. Doh!

My apologies.

Merlin.

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Re: Delay loop generator

· Posted: 03.01.2008 - 12:02 · #5

Hello Avra,

and what about the "uDelay" of AVRco? Or the sDelay? Or the mDelay? Or SysTimers?
Is there really a need for such a delay generator?

rolf

Avra

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Re: Delay loop generator

· Posted: 04.01.2008 - 09:38 · #6

Once I needed that to generate very short and specific signals in interrupt. Another appliance that comes to my mind is tv/video signal generation. Speaking of video, that's one of the reasons I am looking forward for XMEGA. :lupe: With fast 2Msps ADC, frame grabbing is possible without external components (it can all fit in RAM since I need just 1 FPS and 32x32 in 16 grays).

Avra

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Re: Delay loop generator

· Posted: 07.10.2010 - 09:16 · #7

Nice cycle accurate delay: from 1 cycle to 536 seconds.
http://www.avrfreaks.net/index…pe=project

Avra

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Re: Delay loop generator

· Posted: 05.01.2011 - 02:59 · #8

And another one, which produces very compact ASM code:
http://bretm.home.comcast.net/~bretm/avrdelay.html

UPDATE: This is new URL: http://bretmulvey.com/avrdelay.html

Delay loop generator

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