PXS20RM Datasheet, PDF (133/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Device Boot Modes
• No Nexus/JTAG apart from JTAG info for device and mask ID (major and minor) and commands
to temporarily unlock the device with a valid Flash password.
• Boot from Flash main array
— Shadow Block accessible
5.4.3 Serial Boot Loader Mode — Public Password Enabled
• In Serial Boot Loader Mode, if public serial access is allowed, the MCU executes BAM code which
will check for a valid public password on the chosen interface. The interface will be selected via
FAB and ABS pins.
• Nexus/JTAG available if device is not sensored.
• Boot from BAM
• Flash Main Array and Shadow Block access is disabled if device is censored.
5.4.4 Serial Boot Loader Mode — Flash Memory Password Enabled
It is possible to boot in Serial Boot Loader Mode when serial access with password is selected. The MCU
executes BAM code which will check for a valid flash memory password on the chosen interface. If the
password is known, full access to the device is enabled.
• Nexus/JTAG available once the correct password has been received.
• Boot from BAM
• Flash Main Array and Shadow Block access possible once the correct password has been received.
5.4.5 Standby Boot Mode
In Standby-Boot Mode, the MCU can be configured to boot from internal flash memory (Single Chip
mode) or from Standby RAM. If the MCU boots from Standby RAM the reset sequence can be abridged
- in this case the flash memory will not be available. (See RGM block guide for mode selection).
The device security status will be stored in the SSCM Standby area, so debugging will be possible if the
device is unsecured.
5.4.6 Static Mode
Static mode means the device enters the SAFE mode and the processor executes a wait instruction. It is
needed if the device can not boot in the mode which was selected. Access to Nexus and flash memory is
as defined by the boot mode and the security status. Eventually the SWT will cause a reset and restart the
boot search.
PXS20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
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