There is no exact erase time. It is process, temperature, and voltage dependent. There is a datasheet spec for maximum block erase time. Typical block erase time is much shorter than maximum time specification.
Do you want me to search for the datasheet, and look up the maximum block erase time for you... or do you want to do this for yourself?
-- Bob Elkind
SIGNATURE: README for newbies is here: http://forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369
Summary: 1. Read the manual or user guide. Have you read the manual? Can you find the manual? 2. Search the forums (and search the web) for similar topics. 3. Do not post the same question on multiple forums. 4. Do not post a new topic or question on someone else's thread, start a new thread! 5. Students: Copying code is not the same as learning to design. 6 "It does not work" is not a question which can be answered. Provide useful details (with webpage, datasheet links, please). 7. You are not charged extra fees for comments in your code. 8. I am not paid for forum posts. If I write a good post, then I have been good for nothing.