Lpc2000

--- In lpc2000@yahoogroups.com, "James Dabbs" <jdabbs@t...> wrote:
> > Read this post about the RTCK if you want second and subsequent
> > flashing via the secondary JTAG port.
> 
> > http://groups.yahoo.com/group/lpc2000/message/1067
> 
> Ugh..
> 
> What is the *purpose* of RTCK, and why does it interfere with 
flashing the
> chip?  Is this normal, or an LPC bug, or a Nohau issue?  Is there 
ever a
> reason to connect it to the 20-way header?

The RCTK is used by some debuggers for "adaptive clocking", in fact a 
clock feedback system enabling the debugger to run at highest 
possible speed. As far as I know, only a few high-end adapters are 
using this. Here is an answer to the same question from the ARM home 
page:

--------
"RTCK is only used by the JTAG emulator (Multi-ICE or RealView ICE) 
when it is configured in adaptive clocking mode. Adaptive clocking 
ensures that the TCK is slow enough to work with a synthesizable core 
and that its frequency is near the maximum possible. 

In most cases, adaptive clocking is "nice to have" but it is not 
really necessary. You just need to set up TCK with a frequency slow 
enough for your target. In this case you don't need to take RTCK to a 
pin of the ASIC. RTCK on the JTAG connector should be pulled-down."

However, adaptive clocking is necessary when debugging a target with 
variable clock speed. This way the JTAG frequency is always near the 
maximum possible. Without adaptive clocking you would need to set TCK 
at very low frequency, so that it works with all the possible clock 
speeds."
-------

As seen from this, connecting the RTCK is not required. However, I 
have been struggling with the "secondary JTAG problem" myself. And 
unfortunately, not connecting RTCK does not seem to have much effect. 

I have two IAR kick-start boards with the LPC2106 of the same batch. 
On one, the secondary JTAG works OK. On the other, it only works 
after first having used primary connector. See also message 1262. 

Hope Philips can give a good advice!

Jon