Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: airman00 on September 13, 2008, 07:07:58 PM
-
I have a 4 pin oscillator that I want to connect to an 8870 IC .
I am a bit confused on how to wire the 4 pin oscillator. Can someone please help me out?
The oscillator:
(http://www.curiousinventor.com/images/store/products/electronic_components/osc/pinout.jpg)
The schematic
(http://www.qsl.net/oe3mzc/mt8870.gif)
I think the wiring is Output pin(of oscillator) to OSC1 and GND(of oscillator) to OSC2 but I want to make sure.
Thanks,
Eric
-
Your "4 pin oscillator" looks like a DTMF decoder from here.
osc1 & osc 2 are inputs from a crystal
-
Your "4 pin oscillator" looks like a DTMF decoder from here.
osc1 & osc 2 are inputs from a crystal
you misunderstood my question
My crystal is the square oscillator that is pictured. The DTMF decoder is the IC . I wanted to know which of the four pins of the 4 pin oscillator are to be connected to OSC1 and OSC2.
-
The picture you have is a picture of an oscillator, which is different from the crystal in the schematic. A crystal is component inside an oscillator circuit; the oscillator shown is a device that contains a crystal and other circuitry that will produce a square wave when power is applied. On devices that just require a crystal (and usually some caps), like the tone decoder or a PIC, there is additional circuitry inside the device that completes the oscillator circuit, and that external circuitry expects a crystal, not a clock input from an oscillator.
So, in general, you can't sub an oscillator in place of a crystal. In PICs and other microcontrollers, you have to change the configuration to accept a fully formed clock input from an oscillator as opposed to a crystal.
But for this chip, looking at page 4-15 of the spec (http://dhost.info/ky3orr/funkcje/download.php?dzial=pliki&link=dokumentacje/mt8870.pdf), it looks like you can just apply the output of an oscillator to the OSC1 input. Attaching ground to the OSC2 will most likely not work at all. Just leave OSC2 disconnected. The spec also says you need a 3.579545 MHz clock / crystal, so it probably won't work if your oscillator is at a different frequency.
Our crystal page (http://www.curiousinventor.com/store/product/62) explains a bit of the difference between crystals and oscillators, as well as their tradeoffs, and maxim has an even more in depth explantion (http://www.maxim-ic.com/appnotes.cfm/an_pk/2154).
Hopefully I'm answering the right question, and you didn't already know all that.
-
Thanks for the reply
My oscillator is a 3.579545 Mhz oscillator
I'll try what you said about leaving OSC2 disconnected.
Thank you
So in the end this oscillator will work with the 8870 Decoder IC?