Lpc2000

Use of the secondary JTAG has been discussed here before, see ie msg 
1067, 1262 and 1338. I have made a design where only JTAG2 is 
available, just as you suggest, and have not been able to debug the 
design using the JTAG interface. It works OK on other boards if I 
first brefly accesses JTAG1. (The JTAG2 is of course initialised 
according to Philips app note AN10255.)

Tomorrow I am going to meet a representatevi from Philips, and will 
of course discuss this issue with him.

Jon


--- In lpc2000@yahoogroups.com, "embeddedjanitor" 
<charles.manning@t...> wrote:
> --- In lpc2000@yahoogroups.com, Owen Mooney <ojm@s...> wrote:
> > I have added this question as a separate message  as it may 
attract 
> a  
> > different response
> > 
> > I am debating as t which JTAG pins I use in my circuit layout. I 
> can 
> > spare enough ports for the JTAG lines, but not the trace lines.I 
> > understand that enabling the primary JTAG lines also enables the 
> Trace 
> > lines. (there seems to be no way to enable the JTAG lines only 
> according 
> > to p206 in the manual).
> > 
> > This suggests using the secondary JTAG lines only. I will 
probably 
> > purchase the crossworks compiler largely on price (feed back on 
> this 
> > decision is welcome)
> > 
> > Is it practical to
> >     2. layout with only the secondary JTAG "dressed out"
> >     2. write a simple program that initialise the secondary JTAG 
> ports
> >     3. Boot load it and run it.
> >     4. develope and debug (including reload programs) entirely 
from 
> the 
> > secondary JTAG port.
> > 
> > I.e. My question is does the debuging capablity survive all the 
> resets etc
> 
> 
> This is pretty close to what I am planning to do. Indeed there is 
an 
> app note describing what to do.
> 
> I have weritten, and will test in the next 24 hours or so, a small 
> configuration firmware. This is loaded in to flash and executes 
after 
> a reset and configurres the secondary JTAG port then just spins. 
The 
> JTAG debugger then attaches to the secondary JTAG port. NB though, 
> the debugger should not reset the CPU since that would undo the 
> secondary port set up.
> 
> You will be limited in where you then load firmware into flash 
> because, obviously, if you overwrite the secondary port 
configuration 
> code then the pins will no longer be used for JTAG.
> 
> I'll let you know how it goes...
> 
> -- Charles