MC9S08GB60A Datasheet, PDF (52/302 Pages) Freescale Semiconductor, Inc – HCS08 Microcontrollers

Chapter 4 Memory
4.4.3 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 blocks of flash that may be erased. In the 60K version, there are two instances
where the size of a block that is accessible to the user is less than 512 bytes: the first page following
RAM, and the first page following the high page registers. These pages are overlapped by the RAM
and high page registers, respectively.
NOTE
Do not program any byte in the flash more than once after a successful erase
operation. Reprogramming bits in a byte which 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 adhered to, 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 commands. This must
be done only once following a reset.
MC9S08GB60A Data Sheet, Rev. 2
52
Freescale Semiconductor