MC9S08LC60 Datasheet, PDF (53/358 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 4 Memory
4.4.5 Access Errors
An access error occurs whenever the command execution protocol is violated. Any of the following
specific actions will cause the access error flag (FACCERR) in FSTAT to be set. FACCERR must be
cleared by writing a 1 to FACCERR in FSTAT before any command can be processed.
• Writing to a FLASH address before the internal FLASH clock frequency has been set by writing
to the FCDIV register
• Writing to a FLASH address while FCBEF is not set (A new command cannot be started until the
command buffer is empty.)
• Writing a second time to a FLASH address before launching the previous command (There is only
one write to FLASH for every command.)
• Writing a second time to FCMD before launching the previous command (There is only one write
to FCMD for every command.)
• Writing to any FLASH control register other than FCMD after writing to a FLASH address
• Writing any command code other than the five allowed codes (0x05, 0x20, 0x25, 0x40, or 0x41)
to FCMD
• Accessing (read or write) any FLASH control register other than the write to FSTAT (to clear
FCBEF and launch the command) after writing the command to FCMD
• The MCU enters stop mode while a program or erase command is in progress (The command is
aborted.)
• Writing the byte program, burst program, or page erase command code (0x20, 0x25, or 0x40) with
a background debug command while the MCU is secured (The background debug controller can
do blank check and mass erase commands only while the MCU is secure.)
• Writing 0 to FCBEF to cancel a partial command
4.4.6 FLASH Block Protection
The block protection feature prevents the protected region of FLASH from program or erase changes.
Block protection is controlled through the FLASH Protection Register (FPROT). When enabled, block
protection begins at any 512 byte boundary below the last address of FLASH, 0xFFFF. (see Section 4.6.4,
“FLASH Protection Register (FPROT and NVPROT)”).
After exit from reset, FPROT is loaded with the contents of the NVPROT location which is in the
nonvolatile register block of the FLASH memory. In user mode, if FPDIS is set, all FPROT bits are
writeable. In user mode, if FPDIS is clear, the FPS bits are writeable as long as the size of the protected
region is being increased. Because NVPROT is within the last sector of FLASH, if any amount of memory
is protected, NVPROT is itself protected and cannot be altered (intentionally or unintentionally) by the
application software. FPROT can be written through background debug commands, which provide a way
to erase and reprogram protected FLASH memory.
The block protection mechanism is illustrated in Figure 4-4. The FPS bits are used as the upper bits of the
last address of unprotected memory. This address is formed by concatenating FPS7:FPS1 with logic 1 bits
as shown. For example, in order to protect the last 8192 bytes of memory (addresses 0xE000 through
0xFFFF), the FPS bits must be set to 1101 111 which results in the value 0xDFFF as the last address of
unprotected memory. In addition to programming the FPS bits to the appropriate value, FPDIS (bit 0 of
MC9S08LC60 Series Advance Information Data Sheet, Rev. 2
Freescale Semiconductor
PRELIMINARY
53