Does your attempt to send a bit outlast the ringing in the power line? That's why it's speed dependent.
> -----Original Message----- > From: Dave Higton [mailto:[email protected]] > Sent: Friday, March 30, 2012 5:01 PM > To: [email protected] > Subject: Re: [OpenOCD-devel] Fwd: It works! was: Status of PIC32/mips support? > > 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 ------------------------------------------------------------------------------ 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
