MC9S12HZ256 Datasheet, PDF (90/692 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 2 256 Kbyte Flash Module (FTS256K2V1)
2.4.1.4 Illegal Flash Operations
The ACCERR flag will be set during the command write sequence if any of the following illegal steps are
performed, causing the command write sequence to immediately abort:
1. Writing to a Flash address before initializing the FCLKDIV register.
2. Writing to a Flash address in the range 0x8000–0xBFFF when the PPAGE register does not select
a 16 Kbyte page in the Flash block selected by the BKSEL bit in the FCNFG register.
3. Writing to a Flash address in the range 0x4000–0x7FFF or 0xC000–0xFFFF with the BKSEL bit
in the FCNFG register not selecting Flash block 0.
4. Writing a byte or misaligned word to a valid Flash address.
5. Starting a command write sequence while a data compress operation is active.
6. Starting a command write sequence while a sector erase abort operation is active.
7. Writing a second word to a Flash address in the same command write sequence.
8. Writing to any Flash register other than FCMD after writing a word to a Flash address.
9. Writing a second command to the FCMD register in the same command write sequence.
10. Writing an invalid command to the FCMD register.
11. When security is enabled, writing a command other than mass erase to the FCMD register when
the write originates from a non-secure memory location or from the Background Debug Mode.
12. Writing to any Flash register other than FSTAT (to clear CBEIF) after writing to the FCMD
register.
13. Writing a 0 to the CBEIF flag in the FSTAT register to abort a command write sequence.
The ACCERR flag will not be set if any Flash register is read during a valid command write sequence.
The ACCERR flag will also be set if any of the following events occur:
1. Launching the sector erase abort command while a sector erase operation is active which results in
the early termination of the sector erase operation (see Section 2.4.1.3.6, “Sector Erase Abort
Command”)
2. The MCU enters stop mode and a program or erase operation is in progress. The operation is
aborted immediately and any pending command is purged (see Section 2.5.2, “Stop Mode”).
If the Flash memory is read during execution of an algorithm (i.e., CCIF flag in the FSTAT register is low),
the read operation will return invalid data and the ACCERR flag will not be set.
If the ACCERR flag is set in the FSTAT register, the user must clear the ACCERR flag before starting
another command write sequence (see Section 2.3.2.7, “Flash Status Register (FSTAT)”).
The PVIOL flag will be set after the command is written to the FCMD register during a command write
sequence if any of the following illegal operations are attempted, causing the command write sequence to
immediately abort:
1. Writing the program command if the address written in the command write sequence was in a
protected area of the Flash memory.
2. Writing the sector erase command if the address written in the command write sequence was in a
protected area of the Flash memory.
3. Writing the mass erase command while any Flash protection is enabled.
MC9S12HZ256 Data Sheet, Rev. 2.04
90
Freescale Semiconductor