Integrated HW/SW Fault Tree
- IDA
has recently developed the methodology for generating
Integrated Hardware/Software Fault-Trees. This new concept
incorporates the software logic events implemented by a
micro-controller and it’s respective embedded software with
system hardware, and shows the relationships between events
necessary to produce the undesirable top-level failure. In
situations where embedded software controls the system, the
interaction of the software logic with the hardware
failures must be considered in order to discover all the
events that can produce the top-level fault. Many times, as
was demonstrated by the recently completed Integrated Fault
Trees by IDA, hardware failures on the sensor side of the
micro-controller and incorrect commands/status from other
embedded processors generated failure events within the
Fault Tree because of software logic interaction with the
hardware. These failures would not have been detected or
detailed in a hardware-only Fault Tree. The Integrated
Fault Trees lead to some important software changes that
increased the system’s fault-tolerance and provided a tool
to the Reliability Department for assessing future changes.
During the design phase, every system has a reliability goal. Allocations are used to set the goals for various lower-level system elements such that the overall system-level goal can be achieved in an effective way.