Lpc2000

James,

it all started with the assumption that trace emulation would be the 
standard for the ARM devices. Enabling debug on the LPC2104, will 
enable the primary JTAG and the Embedded Trace Macrocell (ETM). This is 
still a very importnat feature which can not be found on most other low 
cost ARM devices.

Unfortunately there has been no option implemented on the LPC210x to 
disable ETM while still having the primary JTAG. As a result, enabling 
the debug channels took away too many pins.

The second JTAG was implemented for test and can actually be used for 
debugging as well.  I do not knwo why you are having problems but what 
I heared from emulator companies like Ashling, Nohau, Hitex, they seem 
to have this interface in use and under control.

Even if would only be for programming, through JTAG it is possible to 
program the device below 10 sec while this is not possible with e.g. 
115,200 baud.  Speed of programming is important to many companies.

btw. all other devices, introduced after the LPC210x have the option to 
enable just JTAG or JTAG and ETM, so no need any more for a secondary 
JTAG.

Hth, Robert


--- In lpc2000@yahoogroups.com, "James Dabbs" <jdabbs@t...> wrote:
> > IIRC, the secondary JTAG is not intended for debugging. It's OK for 
> > programming the flash, of course.
> 
> Leon,
> 
> Thanks for the response.  I guess I don't understand Phillips' goals.
> Why put an entire second JTAG unit on the part when the UART can be 
used
> to program the flash?  I did a project a while back with the LPC2106
> where I was able to debug it with the secondary JTAG port.  The JTAG
> interface on this new board was lifted directly from the first 
project's
> schematic.
> 
> Can anyone from Phillips explain this, what the second port is for, 
and
> why I might be having such intermittent results?
> 
> Thanks.