The TMS320F28P65x 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 TMS320F28P65x MCU or system when a fault
is indicated. Multiple potential fault responses are possible during a fault
indication. The system integrator is responsible to determine which fault response
should be taken to ensure 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 (see Section 4.2.5.1) detects malfunctioning of the device or other system components and powers
down the TMS320F28P65x MCU. From this state, it is possible to re-enter cold
boot to attempt recovery.
- Assertion of XRSn: The
XRSn reset could be generated from an internal or external monitor that detects
a critical fault having potential to violate safety goal. Internal sources
generate this fault response when the TMS320F28P65x MCU is not able to handle
the internal fault condition by itself (for example, CPU1 (master CPU) is not
able to handle NMI by itself). From this state, it is possible to re-enter cold
boot and attempt recovery.
- 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 may be the secondary effect due to a fault condition. In addition,
CPU2 subsystem generates this fault response when it is not able to handle the
internal fault condition by itself (for example, CPU2 is not able to handle NMI
by itself). From this state, it is possible to re-enter warm boot phase and
attempt recovery.
- 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
C28x CPU. ERRORSTS pin will also be asserted along with NMI. Depending on the
system level requirements, the fault can be handled either internal to the
TMS320F28P65x 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.