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Chapter 25 2 Kbyte EEPROM Module (S12XEETX2KV1)
MC9S12XDP512 Data Sheet, Rev. 2.17
1070
Freescale Semiconductor
25.6.1
Unsecuring the MCU in Special Single Chip Mode using BDM
Before the MCU can be unsecured in special single chip mode, the EEPROM memory must be erased
using the following method :
Reset the MCU into special single chip mode, delay while the erase test is performed by the BDM
secure ROM, send BDM commands to disable protection in the EEPROM module, and execute a
mass erase command write sequence to erase the EEPROM memory.
AftertheCCIFflagsetstoindicatethattheEEPROMmassoperationhascompletedandassumingthatthe
Flash memory has also been erased, reset the MCU into special single chip mode. The BDM secure ROM
will verify that the Flash and EEPROM memory are erased and will assert the UNSEC bit in the BDM
statusregister.ThisBDMactionwillcausetheMCUtooverridetheFlashsecuritystateandtheMCUwill
be unsecured. Once the MCU is unsecured, BDM commands will be enabled and the Flash security byte
may be programmed to the unsecure state.
25.7
Resets
25.7.1
EEPROM Reset Sequence
On each reset, the EEPROM module executes a reset sequence to hold CPU activity while loading the
EPROT register from the EEPROM memory according to
Table 25-1
.
25.7.2
Reset While EEPROM Command Active
If a reset occurs while any EEPROM command is in progress, that command will be immediately aborted.
The state of a word being programmed or the sector / block being erased is not guaranteed.
25.8
Interrupts
TheEEPROMmodulecangenerateaninterruptwhenallEEPROMcommandoperationshavecompleted,
when the EEPROM address, data, and command buffers are empty.
NOTE
Vector addresses and their relative interrupt priority are determined at the
MCU level.
Table 25-10. EEPROM Interrupt Sources
Interrupt Source
Interrupt Flag
Local Enable
Global (CCR) Mask
EEPROM address, data, and command buffers empty
CBEIF
(ESTAT register)
CBEIE
(ECNFG register)
I Bit
All EEPROM commands completed
CCIF
(ESTAT register)
CCIE
(ECNFG register)
I Bit