MC9S08GT16A Datasheet, PDF (49/300 Pages) Freescale Semiconductor, Inc – Microcontrollers

• Flexible block protection
• Security feature for FLASH and RAM
• Auto power-down for low-frequency read accesses
Memory
4.4.2 Program and Erase Times
Before any program or erase command can be accepted, the FLASH clock divider register (FCDIV) must
be written to set the internal clock for the FLASH module to a frequency (f_FCLK) between 150 kHz and
200 kHz (see Table 4.6.1). This register can be written only once, so normally this write is done during
reset initialization. FCDIV cannot be written if the access error flag, FACCERR in FSTAT, is set. The user
must ensure that FACCERR is not set before writing to the FCDIV register. One period of the resulting
clock (1/f_FCLK) is used by the command processor to time program and erase pulses. An integer number
of these timing pulses is 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
4.4.3 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.
MC9S08GT16A/GT8A Data Sheet, Rev. 1
Freescale Semiconductor
49