PXS20RM Datasheet, PDF (518/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Fault Collection and Control Unit (FCCU)
22.6.10 FCCU NCF Status Register (FCCU_NCFS0..3)
The FCCU_NCFSx register contains the latched fault indication collected from the non- critical fault
sources. Faults are latched also in the CONFIG state and independently from the enabling or reactions
programmed for the NCF.
No reactions are executed until the FCCU moves in the NORMAL state.
FCCU reacts and moves from the NORMAL state into the ALARM state only if the respective enable bit
for a fault is set in the FCCU_NCFEx register and the respective enable bit for the time-out is set in the
FCCU_TOEx register.
FCCU reacts and moves from the NORMAL or ALARM state into the FAULT state if the respective
enable bit for a fault is set in the FCCU_NCFEx register and the respective enable bit for the time-out is
disabled in the FCCU_TOEx register.
FCCU reacts and moves from the ALARM state into the FAULT state if the time-out (FCCU_TO register)
is elapsed before to recovery the fault.
The time-out is stopped only when the FCCU returns in the NORMAL state.
The status bits of the FCCU_NCFSx register, configured as SW recoverable faults, can be cleared by the
following locked sequence:
• Write the proper key into the FCCU_NCFK register
• Clear the status (flag) bit NCFSx  the opcode OP12 is automatically set into the
FCCU_CTRL.OPR field
• Wait for the completion of the operation (FCCU_CTRL.OPS field)
• Read the FCCU_NCFSx register in order to verify the effective deletion and in case of failure to
repeat the sequence
As result of the above sequence, in addition the FAULT interface provides support to clear the external
FAULT root.
The FCCU moves from the FAULT or ALARM state into the NORMAL state if all the source faults which
caused the transition into the FAULT state has been removed (HW recoverable fault) or cleared via SW
(SW recoverable fault). In case of nested faults that are not all recovered, the FCCU will remain in the
FAULT or ALARM state.
The SW application executes the FCCU_NCFSx read operation by the following sequence:
• to set the OP10 operation into the FCCU_CTRL.OPR field
• to wait for the completion of the operation (FCCU_CTRL.OPS field)
• to read the FCCU_NCFSx register
In case of re-configuration of the FCCU (CONFIG state), before to return in NORMAL state the pending
status bits into the FCCU_NCFSx must be cleared in order to avoid a false transition in ALARM/FAULT
state.
The following errors are ignored:
• to write a wrong key into the FCCU_NCFK register
• to attempt to clear a HW recoverable error
22-18
PXS20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor