MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
13-26
Freescale Semiconductor
NOTE
Flash core reads are done through the BIU. In many cases the BIU will do
page buffering to allow sequential reads to be done with higher
performance. This can create a data coherency issue that must be handled
with software. Data coherency can be an issue after a program or erase
operation, as well as shadow row operations.
In flash normal operating mode, registers can be written and the flash array can be written to do interlock
writes.
Reads attempted to invalid locations will result in indeterminate data. Invalid locations occur when
addressing is done to blocks that do not exist in non 2
n
array sizes.
Interlock writes attempted to invalid locations (due to blocks that do not exist in non 2
n
array sizes), will
result in an interlock occurring, but attempts to program or erase these blocks will not occur because they
are forced to be locked.
See
Section 13.3.2.2, “Low-/Mid-Address Space Block Locking Register (FLASH_LMLR)
,”
Section 13.3.2.3, “High-Address Space Block Locking Register (FLASH_HLR)
“Secondary Low-/Mid-Address Space Block Locking Register (FLASH_SLMLR)
,” for more
information.
13.4.2.2
Read While Write (RWW)
The flash core is divided into partitions. Partitions are always comprised of two or more blocks. Partitions
are used to determine read while write (RWW) groupings. While a write (program or erase) is being done
within a given partition, a read can be simultaneously executed to any other partition. Partitions are listed
in
. Each partition in high-address space comprises of two 128-KB blocks. Note that the shadow
block has unique RWW restrictions described in
Section 13.4.2.5, “Flash Shadow Block
.”
The flash core is also divided into blocks to implement independent erase or program protection. The
shadow block exists outside the normal-address space and is programmed, erased and read independently
of the other blocks. The shadow block is included to support systems that require NVM for security or
system initialization information.
A software mechanism is provided to independently lock or unlock each block in high-, mid-, and
low-address space against program and erase.
13.4.2.3
Flash
Programming
Programming changes the value stored in an array bit from logic 1 to logic 0 only. Programming cannot
change a stored logic 0 to a logic 1. Addresses in locked/disabled blocks cannot be programmed. The user
can program the values in any or all of eight words within a page in a single program sequence. Word
addresses are selected using bits 4:2 of the page-bound word.
Whenever a program operation occurs, ECC bits are programmed. ECC is handled on a 64-bit boundary.
Thus, if only one word in any given 64-bit ECC segment is programmed, the adjoining word (in that
segment) should not be programmed because ECC calculation has already completed for that 64-bit
segment. Attempts to program the adjoining word will probably result in an operation failure. It is
recommended that all programming operations be from 64 bits to 256 bits, and be 64-bit aligned. The
programming operation should completely fill selected ECC segments within the page.
Summary of Contents for MPC5553
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