The TMS320F28P55x MCU product architecture
provides different levels of fault indication from internal safety mechanisms using CPU
interrupt, non maskable interrupt (NMI), assertion of ERRORSTS pin, assertion of CPU input
reset and assertion of warm reset (XRSn). The fault response is the action that is taken by
the TMS320F28P55x MCU or system when a
fault is indicated. Multiple potential fault responses are possible during a fault
indication. The system integrator is responsible for determining which fault response is
taken to verify consistency with the system safety concept. The fault indication, ordered in
terms of severity (device power down being the most severe), is shown in Figure 6-1.
- Device Power Down: This is the
highest priority fault response where the external component (refer to Section 4.2.3.1) detects malfunctioning of the device or other system components and powers down the
TMS320F28P55x MCU. From this state,
re-entering cold boot to attempting recovery is possible.
- Assertion of XRSn: The XRSn reset
can be generated from an internal or external monitor that detects a critical fault having
the potential to violate a safety goal. Internal sources generate this fault response when
the TMS320F28P55x MCU is not able to
handle the internal fault condition solely (for example, CPU1 is not able to handle
NMI solely). From this state,re-entering cold boot and attempting recovery is
possible.
- Assertion of CPU Reset: CPU reset
changes the state of the CPU from pre-operational or operational state to warm boot phase.
The CPU Reset is generated from an internal monitor that detects any security violations.
On a properly working system, the security violations can be the secondary effect due to a
fault condition. From
this state, re-entering warm boot phase and attempting recovery is possible.
- Non Maskable Interrupt (NMI) and
Assertion of ERRORSTS Pin: C28x
CPU supports a non maskable interrupt
(NMI), which has a higher priority than all other interrupts. Each CPU subsystem is equipped with a
NMIWD module responsible for generating NMI to the CPU. ERRORSTS pin is
asserted along with NMI. Depending on
the system-level requirements, the fault can be handled either internal to the TMS320F28P55x MCU using software or
at the system-level using the ERRORSTS pin information.
- CPU Interrupt: CPU interrupt
allows events external to the CPU to generate a program sequence context transfer to an
interrupt handler where software has an opportunity to manage the fault. The peripheral
interrupt expansion (PIE) block multiplexes multiple interrupt sources into a smaller set
of CPU interrupt inputs.