NXP Semiconductors K22F series, Reference Manual, Page: 653 / 1407

29.4.9.1 Command Write Sequence
Flash commands are specified using a command write sequence illustrated in Figure
29-5 . The flash memory module performs various checks on the command (FCCOB)
content and continues with command execution if all requirements are fulfilled.
Before launching a command, the ACCERR and FPVIOL bits in the FSTAT register
must be zero and the CCIF flag must read 1 to verify that any previous command has
completed. If CCIF is zero, the previous command execution is still active, a new
command write sequence cannot be started, and all writes to the FCCOB registers are
ignored.
Attempts to launch a flash command in VLP mode will be ignored. Attempts to launch a
flash command in HSRUN mode will be trapped with the ACCERR flag being set.
29.4.9.1.1 Load the FCCOB Registers
The user must load the FCCOB registers with all parameters required by the desired flash
command. The individual registers that make up the FCCOB data set can be written in
any order.
29.4.9.1.2 Launch the Command by Clearing CCIF
Once all relevant command parameters have been loaded, the user launches the command
by clearing FSTAT[CCIF] by writing a '1' to it. FSTAT[CCIF] remains 0 until the flash
command completes.
The FSTAT register contains a blocking mechanism that prevents a new command from
launching (can't clear FSTAT[CCIF]) if the previous command resulted in an access error
(FSTAT[ACCERR]=1) or a protection violation (FSTAT[FPVIOL]=1). In error
scenarios, two writes to FSTAT are required to initiate the next command: the first write
clears the error flags, the second write clears CCIF.
29.4.9.1.3 Command Execution and Error Reporting
The command processing has several steps:
1. The flash memory module reads the command code and performs a series of
parameter checks and protection checks, if applicable, which are unique to each
command.
Chapter 29 Flash Memory Module (FTFA)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 653