Lpc2000

hello

i have a question regarding timer reset in lpc2138. (pclk = clk / 4)

then I want to reset timer and I set T0TCR = 1. 
when I want to start timer again, I have to set T0TCR to 0 - do I have
to wait for pclk or can I set T0TCR = 0 immediately? 

thx
Zvonko