Clock sources and the SX SMT
Chicago Mike
Posts: 88
So I looked at the cut sheet for the osollators that parallax sells for the SX and I'm a but confused after reading the SX datasheet. For an external oscolator source, you are to include a C1, C2, and RF resistor in each circuit, however SOME·oscolators have the caps built in. Parallax has two 50Mhz oscolators.
The CSTLS50M0X51-B0 (This is the 3 Pin Dip model... Blue)
and the CSTCV50.00MXJ040-TC20 (SMT model)
A few questions?
I can't really find either of these exact numbers in the osolator datasheet. Do BOTH of these have the built in Caps? Or only the DIP model? Both would require the 10K resisitor? The 10K resistor was a new one to me, my circuits had always justed worked without it. I guess I'll start adding it.
Also - I'm moving over·to an SMT board, and one of the stupider questions·is to determine on the SMT component, which pad goes to X1.
Thanks!
Mike.
·
The CSTLS50M0X51-B0 (This is the 3 Pin Dip model... Blue)
and the CSTCV50.00MXJ040-TC20 (SMT model)
A few questions?
I can't really find either of these exact numbers in the osolator datasheet. Do BOTH of these have the built in Caps? Or only the DIP model? Both would require the 10K resisitor? The 10K resistor was a new one to me, my circuits had always justed worked without it. I guess I'll start adding it.
Also - I'm moving over·to an SMT board, and one of the stupider questions·is to determine on the SMT component, which pad goes to X1.
Thanks!
Mike.
·
Comments
If they have 3 leads, then the caps are built in.
It doesn't matter which side to to X1.
The resistor is not always needed. It depends on the resonator.
Bean.
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·The next time you need a hero don't look up in the sky...Look in the mirror.
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Just take a good look at the datasheet on the Parallax website for the SX processors since they list the pinouts for each chip and package style. If you use the SX28 be careful since it has a different pinout than the 28-pin DIP version of the chip. You should also examine the schematic that goes with the SX28 and SX48 Protoboards since they use the surface mount parts and can help.
You have several different clocking options (Internal RC, Resonator, Cyrtal Osc) and you'll need to specify which one in your code. When using a resonator there are a few different settings which help the SX chips with a variety of resonators. I primarily use 4Mhz and 20Mz resonators on most projects with excellent results. If you are laying out your own board and have the room it is a good idea to at least include pads for a 10K surface mount resistor so you can add one later. If you have the space it usually doesn't cost extra to have the extra pads and leaves you the option of adding it.
Robert