S912XEG384J3VA Datasheet, PDF (954/1324 Pages) Freescale Semiconductor, Inc – MC9S12XEP100 Reference Manual Covers MC9S12XE Family

• 4 Kbytes of buffer RAM, consisting of 1 physical RAM block, that can be used as emulated
EEPROM using a built-in hardware scheme, as basic RAM, or as a combination of both
The Flash memory is ideal for single-supply applications allowing for field reprogramming without
requiring external high voltage sources for program or erase operations. The Flash module includes a
memory controller that executes commands to modify Flash memory contents or configure module
resources for emulated EEPROM operation. The user interface to the memory controller consists of the
indexed Flash Common Command Object (FCCOB) register which is written to with the command, global
address, data, and any required command parameters. The memory controller must complete the execution
of a command before the FCCOB register can be written to with a new command.
CAUTION
A Flash word or phrase must be in the erased state before being
programmed. Cumulative programming of bits within a Flash word or
phrase is not allowed.
The RAM and Flash memory may be read as bytes, aligned words, or misaligned words. Read access time
is one bus cycle for bytes and aligned words, and two bus cycles for misaligned words. For Flash memory,
an erased bit reads 1 and a programmed bit reads 0.
It is not possible to read from a Flash block while any command is executing on that specific Flash block.
It is possible to read from a Flash block while a command is executing on a different Flash block.
Both P-Flash and D-Flash memories are implemented with Error Correction Codes (ECC) that can resolve
single bit faults and detect double bit faults. For P-Flash memory, the ECC implementation requires that
programming be done on an aligned 8 byte basis (a Flash phrase). Since P-Flash memory is always read
by phrase, only one single bit fault in the phrase containing the byte or word accessed will be corrected.
26.1.1 Glossary
Buffer RAM — The buffer RAM constitutes the volatile memory store required for EEE. Memory space
in the buffer RAM not required for EEE can be partitioned to provide volatile memory space for
applications.
Command Write Sequence — An MCU instruction sequence to execute built-in algorithms (including
program and erase) on the Flash memory.
D-Flash Memory — The D-Flash memory constitutes the nonvolatile memory store required for EEE.
Memory space in the D-Flash memory not required for EEE can be partitioned to provide nonvolatile
memory space for applications.
D-Flash Sector — The D-Flash sector is the smallest portion of the D-Flash memory that can be erased.
The D-Flash sector consists of four 64 byte rows for a total of 256 bytes.
MC9S12XE-Family Reference Manual Rev. 1.25
Freescale Semiconductor
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