tDVR is measured from the rising edge of /R to the point where the next piece of data is no longer valid and may vary from device to device. If you need the data to be valid for much longer on the output data bus, keep /R LOW longer. Data will be on the output data bus tA after the falling edge of /R, and will remain valid for as long as /R is LOW. The rising edge of /R signifies the end of the current read operation. Data remains on the data bus for tDVR after that point.