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Pic programming

Discussion in 'Electronic Basics' started by Lessie, Apr 18, 2005.

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  1. Lessie

    Lessie Guest

    Does anyone have experience with the jdm/picpgm pic programmer.
    The circuit is available here
    http://www.piclist.com/techref/microchip/MADSEN.gif
    I need some clarifications about some issues,
    1. first, will it work without bc547, and why do we need it.
    2. In the programming data sheet for 12f629
    VIL1 (clock/data) input low level = 0.2Vdd MIN. Is that an
    error, I expected this to be MAX?
     
  2. PeteS

    PeteS Guest

    In this case, the device is being powered from **-5V** (well, it's
    clamped at -5.1) with VDD being ground and VSS at V- (provided by the
    RTS pin),. DTR is providing positive power for the pullup resistor (the
    1.5k). If RB7 is high, then the transistor is off, and CTS is high
    (inactive). When RB7 goes low, it turns on the transistor, pulling CTS
    low, so yes, you need the transistor.

    It's just a standard old NPN ( you could probably use any one of a
    laundry list of such devices - See this page for BC547 details:
    http://www.semiconductors.philips.com/pip/BC547.html)

    As to the VIL1 spec, use the hardware data sheet which shows VIL for
    all except OSC1 at 0.2VDD (MAX). OCS1 is 0.3VDD (MAX) for certain
    operational modes.

    Datasheet available at www.microchip.com

    Cheers

    PeteS
     
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