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SX-Key with external oscillator — Parallax Forums

SX-Key with external oscillator

David BDavid B Posts: 592
edited 2004-12-03 19:56 in General Discussion

I have a question about using an external oscillator with the SX-Key.

My project is using a precision external oscillator to run the Scenix, so the Scenix RTC can be used for timing of other projects.

I have the SX-Tech board with an SX-28 chip, the SX-Key programmer, and a 4 mHz ovenized crystal oscillator with TTL output.

What I did was to assume that the SX-Key could override a moderately high oscillator impedance, so I connected the oscillator's TTL through a 2.2 kOhm resistor to the OSC1 connector on the SX-Tech board.

I used the following programming directives:

DEVICE SX28L, OSCHS, TURBO, STACKX

IRC_CAL IRC_FAST

FREQ 4_000_000

It works just fine. I can program the Scenix with the oscillator running, and the Scenix runs just fine both with and without the SX-Key attached to the SX-Tech board.

But I'm wondering if I'm stressing the SX-Key excessively. I haven't seen any documentation on how to use it with an external oscillator.

Is what I'm doing safe for the SX-Key?

thanks,

David

Comments

  • Ken GraceyKen Gracey Posts: 7,401
    edited 2004-11-30 05:51
    David,

    I talked with Chip who designed the SX-Key and he says "yes it is safe, not at all a problem".

    Shouldn't be a problem. If you destroy the SX-Key I could replace it anyway. But don't do that on purpose please.

    Ken Gracey
    Parallax, Inc.
  • BeanBean Posts: 8,129
    edited 2004-11-30 11:59
    I don't think you can debug like that, but programming should be okay.

    Bean.
  • David BDavid B Posts: 592
    edited 2004-11-30 17:43
    thanks. I've only just started using the SX-Key; I've used an SX-Blitz for a few years, so I'm not used to using the debugger. Maybe if I get a chance, I'll try the debugger.

    David
  • KenMKenM Posts: 657
    edited 2004-12-03 13:05
    You must be very good at programming or have lots of patience. For me personally, If I did not have the debug feature of the SX key I would have given up on the little guy about 5 years ago.
    David B said...
    thanks. I've only just started using the SX-Key; I've used an SX-Blitz for a few years, so I'm not used to using the debugger. Maybe if I get a chance, I'll try the debugger.

    David
  • David BDavid B Posts: 592
    edited 2004-12-03 19:56
    No, actually I'm too stupid. I usually only write programs that are so small that it is obvious what is going on.
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