NXP Semiconductors MC9S08QL4, Reference Manual

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Chapter 4 Memory
MC9S08QL8 MCU Series Reference Manual, Rev. 1
NXP Semiconductors 45
4.5.3 Program and Erase Command Execution
The steps for executing any of the commands are listed below. The FCDIV register must be initialized and
any error flags cleared before beginning command execution. The command execution steps are:
1. Write a data value to an address in the flash array. The address and data information from this write
is latched into the flash interface. This write is a required first step in any command sequence. For
erase and blank check commands, the value of the data is not important. For page erase commands,
the address may be any address in the 512-byte page of flash to be erased. For mass erase and blank
check commands, the address can be any address in the flash memory. Whole pages of 512 bytes
are the smallest block of flash that may be erased.
NOTE
Do not program any byte in the flash more than once after a successful erase
operation. Reprogramming bits to a byte that is already programmed is not
allowed without first erasing the page in which the byte resides or mass
erasing the entire flash memory. Programming without first erasing may
disturb data stored in the flash.
2. Write the command code for the desired command to FCMD. The five valid commands are blank
check (0x05), byte program (0x20), burst program (0x25), page erase (0x40), and mass erase
(0x41). The command code is latched into the command buffer.
3. Write a 1 to the FCBEF bit in FSTAT to clear FCBEF and launch the command (including its
address and data information).
A partial command sequence can be aborted manually by writing a 0 to FCBEF any time after the write to
the memory array and before writing the 1 that clears FCBEF and launches the complete command.
Aborting a command in this way sets the FACCERR access error flag, which must be cleared before
starting a new command.
A strictly monitored procedure must be obeyed or the command will not be accepted. This minimizes the
possibility of any unintended change to the flash memory contents. The command complete flag (FCCF)
indicates when a command is complete. The command sequence must be completed by clearing FCBEF
to launch the command.
Figure 4-2 is a flowchart for executing all of the commands except for burst
programming. The FCDIV register must be initialized before using any flash command. This must be done
only once following a reset.
Table 4-5. Program and Erase Times
Parameter Cycles of FCLK Time if FCLK = 200 kHz
Byte program 9 45

s
Byte program (burst) 4 20

s
1
1
Excluding start/end overhead
Page erase 4000 20 ms
Mass erase 20,000 100 ms