Embedded Software for SoC - Grupo de Mecatrônica EESC/USP

50 Chapter 4
Where:
Flux represents the number of particles reaching the processor per square
unit and time unit;
Time exposure is the duration of the experiment (sec.)
Estimated Upsets represents the number of upsets expected during the entire
radiation experiment.
The obtained results are illustrated in Table 4-8. As expected the number
of observed upsets is double for the hardened CMA program. This is due to
the longer execution under radiation. Even if the number of particles hitting
the processor is higher for the hardened CMA application‚ the number of
undetected upsets is reduced about 3.2 times.
In accordance with the number of estimated upsets occurring in the storage
elements (internal memory and registers) of the DSP processor‚ we calculated
the detection efficiency and error rate for both versions of the CMA
program. Table 4-9 shows that the error rate was reduced about 4 times for
the hardened application while the detection efficiency is higher than 84%‚
thus proving that the error detection technique is efficient in real harsh environments.
Table 4-8.
Experimental results – faults injected in the data area.
Program
Version
#Observed
upsets
Detected-Faults
#Software
detection
#Hardware
detection
Undetected-Faults
#Incorrect
answer
#Loss
sequence
Original CMA
Hardened CMA
48
99
_
84
_
-
47
15
1
-
Table 4-9.
Detection efficiency and error rate for both program versions.
Detection efficiency
Error rate
CMA Original
none
12.40%
CMA Hardened
84.85%
2.96%
4. CONCLUSIONS
In this paper we presented a software error detection method and a tool for
automatic generation of hardened applications. The technique is exclusively
based on the modification of the application code and does not require any
special hardware. Consequently‚ we can conclude that the method is suitable
for usage in low-cost safety-critical applications‚ where the high constraints
involved in terms of memory overhead (about 4 times) and speed decrease