MC68HC11KW1 Datasheet, PDF (89/238 Pages) Motorola, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit

These bits can be read at any time. The value read is the one latched into the register from the
EEPROM cells during the last reset sequence. A new value programmed into this register is not
readable until after a subsequent reset sequence.
Bits in CONFIG can be written at any time if SMOD = 1 (bootstrap or special test mode). If
SMOD = 0 (single chip or expanded mode), these bits can only be written using the EEPROM
programming sequence, and none of the bits is readable or active until latched via the next reset.
4.6.3 RAM and EEPROM security
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The optional security feature protects the contents of EEPROM and RAM from unauthorized
access. Data, codes, keys, a program, or a key portion of a program, can be protected against
access. To accomplish this, the protection mechanism prevents operation of the device in special
test mode. Only resident programs have unlimited access to the internal EEPROM and RAM and
can read, write, or transfer the contents of these memories. To maintain RAM and EEPROM
security, access to external addresses should be restricted to data read or write. Program
execution should not point from the internal resources to the external memory map.
Note:
A mask option on the MC68HC11KW1 determines whether or not the security feature
is made available. If the feature is available, then the secure mode can be invoked by
programming the NOSEC bit to zero. Otherwise, the NOSEC bit is permanently set to
one, disabling security.
If the security feature is present and enabled and bootstrap mode is selected, then the following
sequence is performed by the bootstrap program:
1) Output $FF on the SCI.
2) Turn block protect off. Clear BPROT register.
3) If EEPROM is enabled, erase it all.
4) Verify that the EEPROM is erased; if not, begin sequence again.
5) Write $FF to every RAM byte.
6) Erase the CONFIG register.
If all the above operations are successful, the bootloading process continues as if the device has
not been secured.
MC68HC11KW1
OPERATING MODES AND ON-CHIP MEMORY
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