In message <[email protected]> Attila Kinali <[email protected]> wrote:
> 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. Sorry, I don't think your explanation fits. If you have ground bounce, or ringing caused by reflection, the effect is dependent upon the rise and fall times of the signals, end therefore independent of the clock frequency. Success or failure dependent on the clock frequency must have a different cause. Dave ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ OpenOCD-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/openocd-devel
