What is the difference between the Byte Endurance (ED) and the Number of Total Erase/Write Cycle before Refresh (TREF)?
The Byte Endurance (ED) is rated for each byte-sized memory location. After a byte-sized location has been written 100,000 times, all the other byte-sized locations are still reliable except for that one location.
The Total Number of Erase/Writes Before Refresh (TREF) is a separate counter that tracks the total number of writes to the entire array (all addresses). Once 1,000,000 writes have been performed (regardless of address), all contents need to be refreshed.