Lpc2000

To add to the benefits of RTCK:

How would one enable debug without the RTCK pin?

Excerpt from a Data Sheet:
"RTCK - Returned Test Clock output. Extra signal added to the JTAG port.
Assists debugger synchronization when processor frequency varies.
Bidirectional pin with internal pull-up.
Note: LOW on RTCK while RESET is LOW enables pins P1.31:26 to operate
as Debug port after reset."

Pins P1.31:26 are the JTAG port.

Regards
Joel