MC9S08JM16 Datasheet, PDF (48/386 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 4 Memory
and erase pulses. An integer number of these timing pulses are used by the command processor to complete
a program or erase command.
Table 4-5 shows program and erase times. The bus clock frequency and FCDIV determine the frequency
of FCLK (f_FCLK). The time for one cycle of FCLK is t_FCLK = 1/f_FCLK. The times are shown as a number
of cycles of FCLK and as an absolute time for the case where t_FCLK = 5 μs. Program and erase times
shown include overhead for the command state machine and enabling and disabling of program and erase
voltages.
Table 4-5. Program and Erase Times
Parameter
Byte program
Byte program (burst)
Page erase
Mass erase
1 _{Excluding start/end overhead}
Cycles of FCLK
9
4
4000
20,000
Time if FCLK = 200 kHz
45 μs
20 μs¹
20 ms
100 ms
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. 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 to 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.
MC9S08JM16 Series Data Sheet, Rev. 2
48
Freescale Semiconductor