How to share signal from a ppc440 and ISE

Hello,

I actually implemented a PPC440 inside my existing ISE(11.4) project and 
i would like to share some signals between my entire code in ISE and 
some code inside the PPC.

What i see in XPS is that i can input or output some signals from or to 
ISE if i map them with an address in the UCF.
But i don't want to output or input them, i just want a bus (not in the 
ucf) that can be share between my code in ISE(vhdl) and my code in the 
PPC(c).

I though it should be really simple, but i was not able to find anything 
on the net.

Thanks for your help.