At 06:02 PM 7/1/96 -0500, you wrote:
>>Referencing the PIC16/17 Microcontroller Data Book in the PIC16C84 section
>>subsection 8.2.2 "The PIC16C84 oscillator design requires the use of a
parallel
>>cut crystal. Use of a series cut crystal may give a frequency out of
>>the crystal manufactures specifications"
>
>>Also referencing the PIC16C84 section table 8-2 crystals tested:
>>ECS ECS-40-S-4
>
>>Also referencing the Digikey July-August 1996 catalog page 179
>>Frequency               4.000 Mhz
>>Max Series Load Cap.    Series
>>ECS Part No             ECS-40-S-4
>
>>Could some one explain this to me?
>
>Somebody goofed.
>
>All crystals have two natural resonant frequencies.  When a crystal is modeled
>as a circuit if inductors, capacitors, and resistors; there are two resonant
>circuits, one is an LC series circuit and one is a parallel one.  A parallel
>LC circuit has its maximum impedance at the resonant frequency where a series
>resonant circuit has its minimum impedance at resonance.  Therefore, different
>oscillator ciruit topology is required.
>A "series resonant" crystal is intended for use as if it were the series
>resonant circuit and, if operated in a parallel resonant oscillator like the
>PIC, may oscillate at the parallel frequency (if at all) which is not the rated
>frequency.
>
>>Do I have to look for a Load Cap. rating of series to get a parallel cut
>>crystal and not a series?
>
>No.  You really want a parallel crystal with a load cap rating, usually around
>20 pF.
>
>- Mark Sullivan -
>

It would seem that the S in the part number should mean series.
All the ECS examples at or over 2 Mhz in the Microchip book are ECS-???-S-?
and all those parts are listed as series in the DigiKey Catalog.

So, did DigiKey goof and list the ECS-40-S-4 as series by mistake
or did Microchip goof in their table and list the incorrect crystals
as the kind they tested?

Re-reading your answer again I now take it to mean a good number
would be ECS-40-20-4 with a listed load of 20pf, and so it would
seem the Microchip table (s) are incorrect.

Please correct me if I am wrong.