On 8/6/2010 12:50 PM, Jan-Erik Soderholm wrote:
> On 2010-08-06 18:04, Carl Denk wrote:
>   =20
>> Thanks, Olin, and others that have replied. Olin's link is quite
>> informative, and indicates that ICD is more than just sticking a
>> connector on a board and hooking up 5 wires. I will study in more detail
>> after lunch.
>>
>> The reference to MCLR is, the resistor connected there is labeled as
>> 470 ohm, and then tagged as "typical values".
>>     =20
> I'd say a "typical MCLR" resistor is in the 4.7k - 10k range.
>   =20
At the moment, the MCLR has 10K ohms to Vdd (5 volts). The 470 ohm is in=20
the following circuit from Figure 3-1 of the PICKIT2 manual, "Typical=20
ICSP Application circuit".  In series from ground to +5vdc a 0.1uf cap.=20
 > 10k ohm. The 470 ohm or schottky diode to MCLR. Vpp/MCLR of the=20
PICKIT2 also goes to MCLR. I don't know if I have a schottky diode, I=20
have a bunch of 1n400x and zeners, will change the circuit to the=20
drawing with the 470 ohm.
> I commented in an earlier post on how the RW (WR ?) line is
> connected/used. Any comment on that ?
>
> It *could* be that the LCD (with a floating RW line) is
> driving the data-lines when the PIC isn't actively pulling
> it low (as under reset or when in programming mode).
>   =20
The LCD control lines are as follows:
RS > RA4
RW > RA1
E > RA0
I see that RA4 is open drain, and needs a pull somewhere, probably=20
should be high to not write to the LCD unless intentionally writing.=20
Will try 10k ohms. alternately I could move RS to RA3 that only has an=20
activity LED now.

Thanks on that point.

Thanks everyone too. :)
--=20
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