mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 1133

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

27.4.2.2
The data compress operation will check Flash code integrity by compressing data from a selected portion
of the Flash memory into a signature analyzer.
An example flow to execute the data compress operation is shown in
command write sequence is as follows:
After launching the data compress command, the CCIF flag in the FSTAT register will set after the data
compress operation has completed. The number of bus cycles required to execute the data compress
operation is equal to two times the number of consecutive words to compress plus the number of Flash
blocks simultaneously compressed plus 18 bus cycles as measured from the time the CBEIF flag is cleared
until the CCIF flag is set. Once the CCIF flag is set, the signature generated by the data compress operation
is available in the FDATA registers. The signature in the FDATA registers can be compared to the expected
signature to determine the integrity of the selected data stored in the selected Flash memory. If the last
address of a Flash block is reached during the data compress operation, data compression will continue
with the starting address of the same Flash block. The MRDS bits in the FTSTMOD register will determine
the sense-amp margin setting during the data compress operation.
In order to take corrective action, it is recommended that the data compress command be executed on a
Flash sector or subset of a Flash sector. If the data compress operation on a Flash sector returns an invalid
signature, the Flash sector should be erased using the sector erase command and then reprogrammed using
the program command.
The data compress command can be used to verify that a sector or sequential set of sectors are erased.
Freescale Semiconductor
1. Write to a Flash block address to start the command write sequence for the data compress
2. Write the data compress command, 0x06, to the FCMD register.
3. Clear the CBEIF flag in the FSTAT register by writing a 1 to CBEIF to launch the data compress
command. The address written determines the starting address for the data compress operation and
the data written determines the number of consecutive words to compress. If the data value written
is 0x0000, 64K addresses or 128 Kbytes will be compressed. Multiple Flash blocks can be
simultaneously compressed by writing to the same relative address in each Flash block. If more
than one Flash block is written to in this step, the first data written will determine the number of
consecutive words to compress in each selected Flash block.
command.
Data Compress Command
Since the FDATA registers (or data buffer) are written to as part of the data
compress operation, a command write sequence is not allowed to be
buffered behind a data compress command write sequence. The CBEIF flag
will not set after launching the data compress command to indicate that a
command should not be buffered behind it. If an attempt is made to start a
new command write sequence with a data compress operation active, the
ACCERR flag in the FSTAT register will be set. A new command write
sequence should only be started after reading the signature stored in the
FDATA registers.
MC9S12XDP512 Data Sheet, Rev. 2.17
NOTE
Chapter 27 512 Kbyte Flash Module (S12XFTX512K4V2)
Figure
27-26. The data compress
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