2.10.8 Overflow and Underflow Control

The counter MSB keeps track of the difference between the read address (RA) and the write address (WA). The EMPTY flag is set when the read and write addresses are equal. To prevent underflow, the write address is double-sampled by the read clock prior to comparison with the read address (part A in following figure). To prevent overflow, the read address is double-sampled by the write clock prior to comparison to the write address (part B in the following figure).