On Wed, 05 January 2000, Ian Smith wrote:

>
> On Tue, 4 Jan 2000, James Paul wrote:
> >  Regarding the 4 lead crystals.  Are these actually crystals or
> >  are they canned oscillators?  Do they look like a DIP package
> >  with 1 pin in each corner?  And all corners are rounded except
> >  one which indicates pin 1?
>
> That is it.
>
> >  If this in fact is what you have,
> >  then pin 1 can be either N/C or a TRISTATE pin, Pin 7 is GND,
> >  Pin 8 is OUTPUT, and Pin 14 is Vcc.   If you have the halfsize
> >  parts then Pin 1 is either N/C or TRISTATE. Pin 4 is GND, Pin 5
> >  is OUTPUT and Pin 8 is Vcc.  These are easy to see if they
> >  operate.  Just provide power to pin 8 or 14, Ground pin 4 or 7,
> >  and measure pin 5 or 8 with a scope of frequency counter.  If
> >  you don't see any activity, then pull pin 1 high in either case
> >  to enable the TRISTATE output.
>
> *tinker*  Ahh, I got my PIC running with a ferw of them at different
> speeds.  I was never able to get it to work before, thanks!  I had
> assumed that you needed to take two of those pins into the CLK1
> and CLK2 like a 2-pin crystal, but I see that was incorrect now.
>
> So the 4-pin units have a crystal and an oscillator.  I assume the PIC
> has to have an internal oscillator since it can run a regular 2-pin
> crystal?
>
> Is a resonator equal (with less accuracy) to a 2 or 4 pin osc?
>
> >  If you could supply some of the numbers on the top of the 4 pin
> >  crystals, that may help identify them easier.
>
> CTS SINGAPORE; MXO-55GB-2C; 1.8432 MHZ; 8747 1202
> CTS KNIGHTS INC; MXO 50-2; 19.584 MHZ; 8138 028
> 6N/S TD1145C; 25.175MHz; 8918 NDK JAPAN
> CK1145MC; 28.322200MHz; 8912
>
> Do the 8xxx numbers refer to some common standard?  They all seem to
> have them, even though they are made by different companies.

*****
      Yes, the PIC does have an internal oscillator.  And it can
      be operated at different gains.  That's why you have
      selections for LP, HS, XT, and RC.  All but the RC type
      basically adjust the oscillator for correct bias at the
      operating range.  The RC type utilizes a different type
      of frontend.  You said you had your PIC going at different
      frequencies.  I assume you set your oscillator for either
      HS or XT (Depending on frequency), and fed the output of
      the oscillator module into the OSC1 pin.  OSC2 can be
      left open.

      Regarding the Ceramic Resonator.  It is basically the
      same as a crystal except for the accuracy and the Q.
      But for most uses, has good enough accuracy and more
      importantly, stability, to be used for communications
      purposes.  Their main claim to fame is their small size,
      and lower cost than a crystal.

      The 8XXX numbers are the date code.  ie 8747 is the 47th
      week of 1987 or about Thanksgiving time 1987.  The
      others follow the same general pattern.  I've tried
      several times over the last few minutes to go to the CTS
      website, but it won't connect.  Something must be wrong
      with their server.  Anyway, I can't get on right now.

      Hope this helps you out.

                                           Regards,

                                             Jim




>
> --
> IanSmith@erie.net

jim@jpes.com