I am using the SXKey to program and debug the SX28  on the Professional Dev. Board. I can select 4Mhz as the max. speed, when managed by the SXKey. Is it possible to reach higher frequencies using the SXKey as frequency generator ? Do I need an external resonator for higher frequencies  ?

You can use the SX-Key to generate frequencies all the way up to 50 MHz -- give it a try (change the FREQ directive in your program).

You should be able to use up to 110MHz with the SX-Key.
If you do Run->Clock there is a slider that goes from 400KHz to 110MHz
Bean.

Umm...
The software supports up to 110Mhz, but there was some discussion this past year of that recommended not pushing that high.
I believe that it might overstress the SX-Key or SX-Blitz's internal hardware which includes an SX chip.

Apparently, the SX Ubicom chips are really not engineered to surpass a maximum of 100Mhz and not really well suited over 80Mhz without including specialized EMI and power consumption features.  The heat builds up and the interferances become greater.

When I select Run-Clock I get an error: "Communications Error". Thereafter if I try again I get the error: "SXKey not found on COMx".

If I use the default settings (4Mhz) all works okay and I can program and run programs.

Is this the way to set the SXKey clock frequency ?

I have set FREQ to 16_000_000 and DEVICE to SX28, OSCHS1, TURBO, STACKX, OPTIONX
Is this the right setting for 16 Mhz ?

Another question about frequency. If I change frequencies, say form 4Mhz to 16Mhz, is it expected PULSOUT function will change or will stay constant for the same parameters ?

I believe the compiler uses the FREQ directive to scale the timing specific commands accordingly.

Really? It is too bad because I wanted to increase resolution of PULSOUT by increasing frequency ? :-(
I want to get a 427us pulse. I get some figures next to this but not exactly (by about an 8% offset).
I suppose I will need to do it in assembler with a hardcoded delay if I want better results.

Any suggestion to get better resolution/accuracy with PULSOUT on the SX?

Well, if Im correct you can still do it by setting the FREQ directive to something different than the oscillator you use, but the SX-Key wouldn't work since it uses the FREQ directive to set it's speed.

Inaki,
If you want better resolution from PULSIN then have a look at the compiler output and use it as a guide to creating a custom routine.  If PULSIN (or any other instruction) changed its behavior with a FREQ directive change we would have an unworkable product.  Your full source is included in the compiler output so you'll be able to see how it works -- since you're "rolling your own" you could even make it work with 16 bits.  Just make sure you document how the code works and at what frequency so that anyone else attempting to modify it or run your code at a different FREQ setting can make the appropriate changes.

[Quoting: "Jon Williams (Parallax)"]
Or you could hard-code in place:

 MyPin = 1
 PAUSEUS 427
 MyPin = 0
This will work at any FREQ setting.

Inaki,
 Just make sure the pin is set to be an output first.

 OUTPUT MyPin
 MyPin = 1
 PAUSEUS 427
 MyPin = 0

You may have to lower the 427 value slightly to makeup for the time to change the pin state.

Bean.