PXS20RM Datasheet, PDF (531/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Fault Collection and Control Unit (FCCU)
CONFIG
Configuration exit OR
timeout
Configuration entry
AND NOT (configuration locked)
non-critical fault (masked)
NORMAL
Reset
Non-critical fault
(unmasked AND timeout disabled)
OR critical fault
Non-critical fault
(unmasked AND timeout enabled)
All fault recovered All non-critical
fault recovered
FAULT
Non-critical fault not recovered on time
OR critical fault OR
non-critical fault
ALARM
(unmasked AND timeout disabled)
(Critical fault recovered) AND (any non-critical fault unrecovered)
Figure 22-26. FCCU state diagram
22.7.3 Self-checking capabilities
The FCCU includes some features to support self-checking capabalities of the main FSM in running mode.
The FSM unit is duplicated and its state (internal state and relevant outputs) is checked by 2 RCCx units
(cycle accurate). The following checks (per IRCOSC clock cycle) are provided by the RCCUx units:
• all the FSM outputs and its internal state for the redundant FSM instances are checked to detect
runtime faults on the FSM outputs and its internal state
• parity bits (computed at byte level) on the configuration registers are checked to detect run time
faults on the configuration inputs of the FSM
• parity bits (computed at byte level) on the interface used to clear the FCCU_CFSx and
FCCU_NCFSx status registers
• FCCU_F protocol state in dual-rail, time-switching and bi-stable mode
• common mode signals (handshake interface signals activated only in CONFIG state) congruence
with the FSM state
In case of failure, each RCCx unit provides an interrupt request.
The RCCx state is frozen in a status register.
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
22-31