PXD20RM Datasheet, PDF (1289/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

• Short reset sequence configuration
• Bidirectional reset behavior configuration
• Selection of alternate boot via the backup RAM on STANDBY mode exit (for further mode details,
please see Chapter 29, Mode Entry Module (MC_ME))
• Boot mode capture on RESET deassertion
37.1.3 Modes of operation
The different reset sources are organized into two families: ‘destructive’ and ‘functional’.
• A ‘destructive’ reset source is associated with an event related to a critical—usually
hardware—error or dysfunction. When a ‘destructive’ reset event occurs, the full reset sequence is
applied to the device starting from PHASE0. This resets the full device ensuring a safe start-up
state for both digital and analog modules. ‘Destructive’ resets are
– Power-on reset
– 1.2V low-voltage detected (power domain #0)
– 1.2V low-voltage detected (power domain #1)
– Software watchdog timer
– 2.7V low-voltage detected
• A ‘functional’ reset source is associated with an event related to a less-critical - usually
non-hardware - error or dysfunction. When a ‘functional’ reset event occurs, a partial reset
sequence is applied to the device starting from PHASE1. In this case, most digital modules are reset
normally, while analog modules or specific digital modules’ (e.g. debug modules, flash modules)
state is preserved. ‘Functional’ resets are
– external reset
– JTAG initiated reset
– CPU reset
– software reset
– checkstop reset
– FMPLL0 fail
– FXOSC frequency lower than reference
– CMU0 clock frequency higher/lower than reference
– 4.5V low-voltage detected
– FMPLL1 fail fatal error
When a reset is triggered, the MC_RGM state machine is activated and proceeds through the different
phases (i.e. PHASEn states). Each phase is associated with a particular device reset being provided to the
system. A phase is completed when all corresponding phase completion gates from either the system or
internal to the MC_RGM are acknowledged. The device reset associated with the phase is then released,
and the state machine proceeds to the next phase up to entering the IDLE phase. During this entire process,
the MC_ME state machine is held in RESET mode. Only at the end of the reset sequence, when the IDLE
phase is reached, does the MC_ME enter the DRUN mode.
Freescale Semiconductor
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
37-13