PXS20RM Datasheet, PDF (1257/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Reset Generation Module (MC_RGM)
NOTE
If a masked ‘functional’ reset event which is configured to generate a SAFE
mode/interrupt request occurs during PHASE1, it is ignored, and the
MC_RGM will not send any safe mode/interrupt request to the MC_ME.
41.4.6 Boot mode capturing
The MC_RGM samples PA[4:2] whenever RESET_B is asserted until five IRCOSC clock cycles before
its deassertion edge. The result of the sampling is used at the beginning of reset PHASE3 for boot mode
selection and is retained after RESET_B has been deasserted for subsequent boots after reset sequences
during which RESET_B is not asserted.
NOTE
In order to ensure that the boot mode is correctly captured, the application
needs to apply the valid boot mode value the entire time that RESET_B is
asserted.
NOTE
RESET_B can be low as a consequence of the internal reset generation.
This will force re-sampling of the boot mode pins. (See Table 41-10 for
details.)
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
41-25