Lpc2000

I've just got a 2119,and I wonder how to enter the Debug mode of 2119.
Although the "user manual" said that "LOW on RTCK while RESET is LOW,
enables pins P1.31:26 to operate as Debug port after reset",I'm not 
sure whether the RTCK pin should be LOW all the times or just for a 
while when RESET is LOW?
Thank you for replying:)