Lpc2000

The External Match Register Uses the EMO-EM3 as outputs bits 0,1,2,3
The documentation states These bits reflect the state of the outputs, 
If thats the case then you should not write to these bits correct????
So the LSB 0-3 should not be written to in the external match register 
correct.??? I'm lost on this one?? 
Anybody got any idea on how or just what the purpose of these bits are 
other than just an output pin that goes high, low, or toggle????
I can see reading these bits for status of the output, but writting to 
these bits I don't understand unless it's an enable, but if thats the 
case, then how can you read the output status???
lost in bit land.