MC68HC08AZ32A Datasheet, PDF (41/312 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Read-Only Memory (ROM)
During a subroutine call, the CPU uses 2 bytes of the stack to store the return address. The stack pointer
decrements during pushes and increments during pulls.
NOTE
Care should be taken when using nested subroutines. The CPU may
overwrite data in the RAM during a subroutine or during the interrupt
stacking operation.
2.6 Read-Only Memory (ROM)
The user ROM consists of up to 32, 256 bytes from addresses $8000–$FDFF. The monitor ROM and
vectors are located from $FE20–$FF5F.
Fifty-two user vectors, $FFCC–$FFFF, are dedicated to user-defined reset and interrupt vectors.
Security has been incorporated into the MC68HC08AZ32A to prevent external viewing of the ROM
contents⁽¹⁾. This feature is selected by a mask option and ensures that customer-developed software
remains propriety. See Chapter 10 Mask Options.
2.7 Electrically Erasable Programmable Read-Only Memory (EEPROM)
The 512 bytes of EEPROM are located at $0800-$09FF and can be programmed or erased without an
additional external high voltage supply. The program and erase operations are enabled through the use
of an internal charge pump. For each byte of EEPROM, the write/erase endurance is 10,000 cycles.
Features include:
• 512 bytes nonvolatile memory
• Byte, block, or bulk erasable
• Nonvolatile EEPROM configuration and block protection options
• On-chip charge pump for programming/erasing
• Program/erase protection option
• Read protection option
• AUTO bit driven programming/erasing time feature
2.7.1 EEPROM Configuration
The 8-bit EEPROM nonvolatile register (EENVR) and the 16-bit EEPROM timebase divider nonvolatile
register (EEDIVNVR) contain the default settings for the following EEPROM configurations:
• EEPROM timebase reference
• EEPROM program/erase protection
• EEPROM block protection
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the ROM difficult for
unauthorized users.
MC68HC08AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
41