Author Topic: Looking for Crystal Oscillators for 8051  (Read 2773 times)


Looking for Crystal Oscillators for 8051
« on: April 16, 2013, 09:04:34 PM »
I am working on a midi based stompbox pedal and between the internet and the library is eagle, cannot find for the life of me a compatible oscillator for an 8051.  I wanted to double check on the package types, but have no clue of the difference between a UM-5 package and a UM-1 package.  To make matters worse, most of the eagle components for said packages are all three pin.  I believe the third pin is a ground connection for noise reduction.  If I was going to use external caps to ground for the crystal should you or shouldn't you use said ground connection or?  Honestly I am really confused when it comes to crystals, it is the only thing I am not aware of when it comes to microcontrollers.

Also, considering the crystal frequency and baud rate, I would like to double check, but do midi based microcontrollers run on 12MHz instead of the standard 8051 frequency of 11.0592MHz and if the clock is indeed 12MHz, how can the baud rate for midi be 9600, or is it?  Obviously these are things I am going to need to calculate when I am writing the program so it is kind of important to know what hardware I am going to be using.


Re: Looking for Crystal Oscillators for 8051
« Reply #1 on: April 17, 2013, 01:43:20 AM »
Heres a handy page that generates tables of baud rates with dividers for given crystal frequencies (along with % of error)

I assume the difference is just in height, otherwise most of the through hole crystals I seem seem to all be 3 pcb holes wide. By third connection I'm assuming they mean the actual case, grounding it helps with stability  (both mechanical and in regard to electrical interference).


Re: Looking for Crystal Oscillators for 8051
« Reply #2 on: April 22, 2013, 08:40:11 AM »
three pin devices in the oscillator category are typically 'resonators'. it's usually a package containing an oscillating element and two capacitors connected back to ground as they usually are in oscillator circuits. Crystals have only two leads and depending on the application, you are required to provide the load capacitors and/or limiting resistors.

check Mouser under Frequency control and timing devices. You'll see separate Crystal and resonator categories there.

Nothing witty yet ...