Maybe use a PWM to generate one clock, and generate the other in code?

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

----- Original Message -----
From: Dan Michaels <oricom@USWEST.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, November 10, 2000 3:38 PM
Subject: Re: [PIC]: Generating variable frequency square waves


> Hi John,
>
> This is not quite what you are after, but ----
>
> Since you are using a '74, if you want "rock-steady" pulsetrain
> output, not dependent upon any software, you might also look at
> using the PWM modules. You can only get one frequency this way,
> but you can get 2 different pulsewidths or duty cycles.
>
> With 10Mhz xtal, you can get 2.500 Mhz down to 600 hz - it obviously
> scales by xtal value. Frequency selections are a little "grainy"
> on the high end - 2.5, 1.25, .8333, .625, .500, .4166, .357, .275,
> .250, etc. However, rock-steady pulse generation.
>
> This works because the PWM registers on the PICs are totally
> programmable for any pulse width and pulse periods. For more info,
> I have an appnote on this:
>
> "AN-ECD06 - Precision 50-nsec Pulse Generation Using a PIC16C63"
>
> http://www.users.uswest.net/~oricom/appnotes.htm
>
> regards,
> - Dan Michaels
> Oricom Technologies
> http://www.users.uswest.net/~oricom
> ===================================
>
>
>
>
> tom sefranek wrote:
> >Hint...
> >
> >Read about the TIMERS.
> >
> >john darcy wrote:
> >
> >> Hi, well for a start sorry about my first post...i
> >> didn't make things too clear. I checked the archives
> >> but couldn't find anything that helped.
> >>
> >> What I need is some code (pic assembly) for a PC16C74A
> >> to implement the following....
> >>
> >> **Generate two square wave outputs, each with a 50%
> >> duty cycle. Also I want to be able to vary the
> >> frequency of these signals independently of one and
> >> other from about 1KHz to 2MHz or as close as I can get
> >> to these limits.
> >>
> >> **The frequency of each square wave will be entered on
> >> a PC keyboard and sent via the serial port to the PIC
> >> but at the moment my main problem is trying to set up
> >> the square waves themselves.
> >>
> >> If anyone has some code that I could use to generate
> >> these square waves and set their frequencies by say
> >> putting a value in the appropriate register I'd really
> >> appreciate it. Thanks a million,
> >>                                 John.
> >>
>
> --
> http://www.piclist.com hint: The PICList is archived three different
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>
>
>
>

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