| ??? 03/30/09 08:15 Read: times |
#163986 - Not tied directly to MCU Responding to: ???'s previous message |
Joseph Hebert said:
Hi Jecksons,
The 4-pin oscillator you're refering to is a standalone circuit that has a crystal in it. That's why it needs Vcc and GND. When powered up, it energizes a crystal and produces an output signal (relative to ground). That signal is then applied to one of the XTAL pins of your µ-controller and serves as the clock. If you choose to use a crystal instead of an oscillator, then you must connect both pins of the crystal to both of the XTAL pins on your µ-controller, along with a couple of capacitors. The internal circuitry of the µ-controller will then stimulate the crystal (assuming you've chosen your capacitors well) and produce the clock signal on the necessary pin. Refer to your documentation for capacitor values. Joe Hai The MCUs have capability to match not only Xtal and 2 capasitors. The Osc1 input could get signal oscillator without needed osc2 pin. Is there something like another 3 pins chip? which 2 pins for Xtal and capasitors then 1 pin output high resistance signal? or must used TTL/CMOS chip without another option. Thank you Jeckson Ben |
