[ethmac] fifo reset

[zou.yixin@zte.com.cn]

Hi,
  In my design ,Fifo is used to store the frame data that is to be transmitted.When col occurs during transfer,
the frame will be re-transmitted.I want to reset the read point(read address) only when col occurs.Then it is not 
neccessary to transfer data from memory to fifo.But i can not find any core in xilinx that provides the function to 
reset read point.Who can give me a suggestion on how to reset the read point? Or any better methods ?
Thanks.
  yxzhou