Re: crystal in mcs
when we design any control or communication circuit you have to calculate the clock you need to execute your program so the clock change from circuit to circuit to control the clock you change the crystal for know more about crystal you can visite
**broken link removed**
about APPLICATION NOTE 726
Specifying Quartz Crystals
the capacitor due to prevent noise if you use breadboard you can use crystal without capcitor
yes you can change the capcitor but in small range about 33pf