AN2400 Freescale Semiconductor / Motorola, AN2400 Datasheet - Page 23

• Manufacturer Part Number: AN2400
• Description: HCS12 NVM Guidelines
• Manufacturer: Freescale Semiconductor / Motorola

Freescale Semiconductor, Inc.
AN2400/D
Flash Memory
ends at the top of the Flash block and is extendable towards lower addresses.
The lower and upper protected blocks do not meet up. In general, the upper
protected area of Flash Block 0 is used to hold bootloader code since it
contains the reset and interrupt vectors. The lower protected area of Block 0
and the protected areas of the other Flash blocks can be used for critical
parameters that would not change when program firmware is updated.
On some microcontrollers, it is also possible to protect the area between the
upper and lower areas. This feature allows a small area of Flash to remain
unprotected when using Flash to emulate EEPROM. Refer to the relevant
Flash Block Guide for details.
Trying to program or erase any of the protected areas will result in a protection
violation error and bit PVIOL will be set in the Flash Status Register FSTAT. A
mass erase of an entire Flash block is only possible if protection of that block
is fully disabled.
MOTOROLA
HCS12 NVM Guidelines
23
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