EEPROM-2 Memory
Functional Description
MC68HC908AZ60A — Rev 2.0 Technical Data
MOTOROLA EEPROM-2 Memory 113
As the CGMXCLK or bus clock is user selected, the EEPROM-2
Timebase Divider Register must be configured with the appropriate
value to obtain the 35 µs. The timebase divider value is calculated by
using the following formula:
EE2DIV= INT[Reference Frequency(Hz) x 35 x10
-6
+0.5]
This value is written to the EEPROM-2 Timebase Divider Register
(EE2DIVH and EE2DIVL) or programmed into the EEPROM-2
Timebase Divider Non-Volatile Register prior to any EEPROM program
or erase operations(see EEPROM-2 Configuration on page 112 and
EEPROM-2 Timebase Requirements on page 112).
7.5.3 EEPROM-2 Program/Erase Protection
The EEPROM has a special feature that designates the 16 bytes of
addresses from $06F0 to $06FF to be permanently secured. This
program/erase protect option is enabled by programming the EEPRTCT
bit in the EEPROM-2 Non-Volatile Register (EE2NVR) to a logic zero.
Once the EEPRTCT bit is programmed to 0 for the first time:
• Programming and erasing of secured locations $06F0 to $06FF is
permanently disabled.
• Secured locations $06F0 to $06FF can be read as normal.
• Programming and erasing of EE2NVR is permanently disabled.
• Bulk and Block Erase operations are disabled for the unprotected
locations $0600-$06EF, $0700-$07FF.
• Single byte program and erase operations are still available for
locations $0600-$06EF and $0700-$07FF for all bytes that are not
protected by the EEPROM-2 Block Protect EEBPx bits (see
EEPROM-2 Block Protection on page 114 and EEPROM-2
Array Configuration Register on page 121)
NOTE: Once armed, the protect option is permanently enabled. As a
consequence, all functions in the EE2NVR will remain in the state they
were in immediately before the security was enabled.
