Are the 4 and 50 mhz resonators required for sx chip usage?

computer_geek

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Title

Bean

I depends on what you want to do.
The SX will run @ 4MHz, 1MHz, 128KHz, and 32KHz on it's own internal clock.
BUT...The internal clock is not acurate enough for sensitive timing (like serial communications).

Bean.

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Steel

Just adding:

The internal oscillator has a max of 4Mhz.· If you want anything more than that, then you will need an external oscillator.

Make sure you have a 'disconnect' in your circuit (jumpers)·for when you need to program the SX.· If you are using an external oscillator it must not be connected when you program your chip because it will interfere with the program download.

LoopyByteloose

Parallax is just trying to keep its parts inventory simple - a fast resonator and slow resonator.

You can run SXes on just about any crystal or oscillator up to 80Mhz, maybe 100Mhz too.
You might even use a 555 to run it or a flip-flop circuit. You can borrow timing from another device too.

Resonators are just the easiest, smalllest device to use. 0.5% tolerance is available while the slow internal oscilator varies up to 6-7% due to temperature changes [noparse][[/noparse]no good for a UART].

Crystals can provide even tigher control, but gosh.....
Crystals come in series cut and parallel cut. Crystals come in a lot more frequencies too.
You might like a crystal to deal with a particular oddball frequency [noparse][[/noparse]like video timing]

But it gets complicated, while series cut appear to not require additional capacitors, the parallel ones do require two caps.
Then the problem is how to find out which value those capacitors should be.

And, how do you know your crystal is series or parallel cut? From what I have read, generally, series cut are limited to about 20Mhz. Over that it is likely a parallel cut, but below that - well, I don't know.

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···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

hammerhead74000

Or you could use a TTL oscilator...

Guenther Daubach

BTW: For programming, it is not necessary to disconnect the resonator but it must be disconnected for debugging, or when you want to clock the SX from the SX-Key.

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G