Carl Denk wrote:
> I am driving a 44780 LCD display 4 bit data mode with an 18F1320 with
> in the common way, the 4 data signals are driven by RB4 - RB7. Using a
> PICKIT2 to program and debug the board. RB7 and RB6 are dual function
> also as PGC and PGD. I get an error when trying to program or debug
> with this setup. The error goes away  if I unplug the display ribbon
> cable.

My ICSP writeup at http://www.embedinc.com/picprg/icsp.htm goes into some o=
f
these issues.

> The PICKIT2 manual shows resistors going th the application on these 2
> signals, with the MCLR signal having "470 ohm*" resistor and below "
> *Typical".  Should I interpret that, that my 2 resistors should be 470
> ohm also? And will that drive the LCD OK? Or is there a better way of
> doing this?

What does MCLR have to do with all this?  I thought the problem was PGC and
PGD also used as data lines during normal operation.

> I do have a stand alone programmer, but the requires pulling the chip
> each time. And pulling the ribbon cable each time isn't good either.

You shouldn't have to do either.  Programmers designed for in-circuit use
generally set the PGC and PGD lines to high impedence when not programming
for exactly this reason.  Our USBProg and USBProg2 definitely do that.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.