Pic programming

[Lessie]

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?

 

[PeteS]

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