Data hold time

Question: Data that is read out of a synchronous dual-port holds valid for a minimum period of "tDC". What is the maximum value? How long will the data read out (Qn) be available on the data lines after the clock edge?

 

Answer:


The minimum amount of time that the data will be valid after the clock goes high is specified on the datasheet as the value tDC. We do not have a set maximum value for tDC because it varies; the important timing characteristic here is that data will stay valid for a minimum amount of time. Generally speaking, datasheet specifications are what we guarantee the part to do. In other words, we can guarantee that data will be there for at least tDC. The device that is latching the data should be designed to use this guaranteed window of opportunity to catch the data.

For more information about how synchronous dual-ports work, please refer to the application note "Understanding Synchronous Dual-Port RAMs".