Freescale Semiconductor, Inc.
Flash Memory
Operation
that the program/erase process is reliable, and also to provide the
longest possible life expectancy. This method requires stopping the
program/erase sequence at periods of t
(t
for erasing) to
PPULSE EPULSE
determine if the Flash EEPROM is programmed/erased. After the
location reaches the proper value, it must continue to be
programmed/erased with additional margin pulses to ensure that it will
remain programmed/erased. Failure to provide the margin pulses could
lead to corrupted or unreliable data.
Program/Erase Sequence — To begin a program or erase sequence
the external V voltage must be applied and stabilized. The ERAS bit
FP
must be set or cleared, depending on whether a program sequence or
an erase sequence is to occur. The LAT bit will be set to cause any
subsequent data written to a valid address within the Flash EEPROM to
be latched into the programming address and data latches. The next
Flash array write cycle must be either to the location that is to be
programmed if a programming sequence is being performed, or, if
erasing, to any valid Flash EEPROM array location. Writing the new
address and data information to the Flash EEPROM is followed by
assertion of ENPE to turn on the program/erase voltage to
program/erase the new location(s). The LAT bit must be asserted and
the address and data latched to allow the setting of the ENPE control bit.
If the data and address have not been latched, an attempt to assert
ENPE will be ignored and ENPE will remain negated after the write cycle
to FEExxCTL is completed. The LAT bit must remain asserted and the
ERAS bit must remain in its current state as long as ENPE is asserted.
A write to the LAT bit to clear it while ENPE is set will be ignored. That
is, after the write cycle, LAT will remain asserted. Likewise, an attempt
to change the state of ERAS will be ignored and the state of the ERAS
bit will remain unchanged.
The programming software is responsible for all timing during a program
sequence. This includes the total number of program pulses (n ), the
PP
length of the program pulse (t
), the program margin pulses (p )
m
PPULSE
and the delay between turning off the high voltage and verifying the
operation (t ).
VPROG
The erase software is responsible for all timing during an erase
sequence. This includes the total number of erase pulses (e ), the
m
68HC(9)12D60 — Rev 4.0
MOTOROLA
Advance Information
107
Flash Memory
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