In a standard FIFO, EMPTY is deasserted when one or more words are available to be read from the FIFO. By asserting RDEN, the next piece of data appears on the DOUT bus after the next rising edge of RDCLK. When the EMPTY flag is asserted, no more data is available to be read, and any additional reads cause RDERR to assert after the next RDCLK edge. See the following figure.
Figure 1. Standard FIFO Interface
