SOPC ERROR: Cannot have an associated clock

Traditionally you have two ways oy handling timing on an avalon slave interface.

The first way is to use fixed timing. In that case you only use the read and write signals, with no acknowledge, and you specify in the component builder how many cycles are necessary for a read or a write operation.

The other one is to use the waitrequest signal. In that case, as soon as you have the read or write request, you assert waitrequest, and the master will wait. When the read or write operation is finished, de-assert waitrequest. I guess this is the closest to the acknowledge that you want to implement.

All this is well described in the avalon interface specification (http://www.altera.com/literature/manual/mnl_avalon_spec.pdf).