Graeme Odgers wrote:
>Hello Nigel and Dan,
>
>Dan I agree with you, I've been using C'84 chips with the Dontronics parallel
>programmer for a couple of years and have had no problems with Nigel's
>software.
>
>This year we have been using the 20MHz F84A's - and have they been a pain.
>Some chips program just as easy as the C84's, but the majority do not!!
>
>To get them to program I have placed a small 330pF capacitor on the RB6 and
>RB7 to ground.  This has worked with some success for most chips, but there
>are a few stubborn chips that do not program very reliably.
>
>Nigel, is there a way to change the programming time (burn period) in your
>software?
>


Hi Graeme,

Great - some good experience with this problem, and a fix thrown
in to boot. I wonder if the problem is risetime or ringing on the
RB6 and RB7 datalines? What do the signals look like before and after
using the 330pF caps? I also wonder if ground routing might not be
an issue here.

I have an EPIC programmer and have had no problems programming
'C84s, 'F84s, or the newer '87x chips.

But I have a similar problem with driving an A/D with 6Mhz
SPI. Still don't have a perfect handle on it, since the problem
disappears when I attach the scope probe. Tried RC filters
in the lines --> helps but not on every board. Tried rearranging
gnds --> no help. Touching with finger fixes the problem,
regardless of RC filters --> ????????. Ended up that using a
4.7K resistor to gnd on certain pins fixed the problem -->
termination issue, I guess ????. Still scratching.

best regards,
- Dan Michaels
Oricom Technologies
http://www.users.uswest.net/~oricom
===================================

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu