5.2 Erase/Write Enable (EWEN)
To ensure data integrity, the part automatically goes into the Erase/Write
Disable (EWDS) state when power is first applied. An Erase/Write Enable
(EWEN) instruction must be executed first before any programming
instructions can be carried out.
Note: Once in the write-enabled state,
programming remains enabled until an
EWDS instruction is executed or
VCC power is removed from the part.