With the Cypress S25FL1-K device, is it possible to READ from the FLASH during an active PROGRAM or ERASE operation?
While the S25FL1-K is being programmed or erased, all other commands, except for Read Status Register and Suspend commands, will be ignored until the program or erase cycle has completed. When the Status Register is being written, all commands except for Read Status Register will be ignored until the Status Register write operation has completed. In other words, all attempts to read the contents of the S25FL1-K's memory array during an active program, erase, or a write cycle (embedded operations) are ignored. The current embedded operation will continue to execute without any affect.
In fact, this is a general rule for all “single-bank” flash devices. There are some flash devices that are “multi-bank”, wherein the scope of the busy state due to in-progress program or erase is limited to one bank. However, many flash chip designs have only one bank—like S25FL1-K—so when that bank becomes busy it is no longer possible to read data from the flash array.