MC9S12XD256MAL Datasheet, PDF (1167/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Chapter 28 256 Kbyte Flash Module (S12XFTX256K2V1)
28.4.1.2 Command Write Sequence
The Flash command controller is used to supervise the command write sequence to execute program,
erase, erase verify, erase abort, and data compress algorithms.
Before starting a command write sequence, the ACCERR and PVIOL flags in the FSTAT register must be
clear (see Section 28.3.2.6, “Flash Status Register (FSTAT)”) and the CBEIF flag should be tested to
determine the state of the address, data and command buffers. If the CBEIF flag is set, indicating the
buffers are empty, a new command write sequence can be started. If the CBEIF flag is clear, indicating the
buffers are not available, a new command write sequence will overwrite the contents of the address, data
and command buffers.
A command write sequence consists of three steps which must be strictly adhered to with writes to the
Flash module not permitted between the steps. However, Flash register and array reads are allowed during
a command write sequence. The basic command write sequence is as follows:
1. Write to a valid address in the Flash memory. Addresses in multiple Flash blocks can be written to
as long as the location is at the same relative address in each available Flash block. Multiple
addresses must be written in Flash block order starting with the lower Flash block.
2. Write a valid command to the FCMD register.
3. Clear the CBEIF flag in the FSTAT register by writing a 1 to CBEIF to launch the command.
The address written in step 1 will be stored in the FADDR registers and the data will be stored in the
FDATA registers. If the CBEIF flag in the FSTAT register is clear when the first Flash array write occurs,
the contents of the address and data buffers will be overwritten and the CBEIF flag will be set. When the
CBEIF flag is cleared, the CCIF flag is cleared on the same bus cycle by the Flash command controller
indicating that the command was successfully launched. For all command write sequences except data
compress and sector erase abort, the CBEIF flag will set four bus cycles after the CCIF flag is cleared
indicating that the address, data, and command buffers are ready for a new command write sequence to
begin. For data compress and sector erase abort operations, the CBEIF flag will remain clear until the
operation completes. Except for the sector erase abort command, a buffered command will wait for the
active operation to be completed before being launched. The sector erase abort command is launched when
the CBEIF flag is cleared as part of a sector erase abort command write sequence. Once a command is
launched, the completion of the command operation is indicated by the setting of the CCIF flag in the
FSTAT register. The CCIF flag will set upon completion of all active and buffered commands.
28.4.2 Flash Commands
Table 28-18 summarizes the valid Flash commands along with the effects of the commands on the Flash
block.
Table 28-18. Flash Command Description
FCMDB
0x05
NVM
Command
Erase
Verify
Function on Flash Memory
Verify all memory bytes in the Flash block are erased.
If the Flash block is erased, the BLANK flag in the FSTAT register will set upon command
completion.
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MC9S12XDP512 Data Sheet, Rev. 2.21
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