Moin,
On Thu, 29 Mar 2012 17:02:50 +0200
Uhrheber <[email protected]> wrote:
> On 29.03.2012 11:38, salvador wrote:
>
> >
> > adapter_khz 500
>
> It works now!
> The above statement was the problem.
> I had to go down to 300kHz to make it work.
Oh, that's a quite common problem. When i first try to bring up a board
i always use 1kHz as JTAG clock. Why? Because i don't know how fast the
system can go and i want to keep the number of problem sources at a minimum.
Later, when i know that JTAG works, i can increase the speed.
> I don't know what's the cause of this.
> Ok, it's a prototype board without ground plane, but the wires between
> adapter
> and PIC are very short, and the PicoTAP is directly plugged to the
> board, without any
> cable.
This sounds like you have "ground bounces" or something similar.
Add thicker wires for VCC and GND, and use more ceramic decoupling
capacitors.
Also, if you have any "high power" components, like external DRAM
or Flash, use MORE capacitors and THIKER wires. These beasts have
high peak currents that make them difficult to use on breadboards.
An alternative would be to use a copper plate (or an raw PCB) and
solder the components on small carrier prints... or upside down.
This way you get a better ground connection, as you have a plane
underneath.
Attila Kinali
--
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin
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