Embedded Software for SoC - Grupo de Mecatrônica EESC/USP

Detecting Soft Errors by a Purely Software Approach 49
Table 4-5. Detection efficiency and error rate for both program versions.
Detection Efficiency ()
Error Rate (t)
CMA Original
none
17.89 %
CMA Hardened
55.97 %
1.18%
code. This results show that about 60% of injected faults changing the
program’s behavior have been detected and a significant decrease of error
rate (about 17 times) for the hardened application.
3.1.3. Fault injection in the data memory area
When faults have been injected in the data segment area (results illustrated
in Table 4-6)‚ the hardened CMA program was able to provide 100% detection
efficiency. It is important to note that output data (program results) were
located in a “non targeted” zone aiming at being as close as possible to a real
situation where output samples will get out the equalizer by means of parallel
or serial ports without residing in any internal RAM zone.
Table 4-6. Experimental results – faults injected in the data segment area.
Program version
#Injected
faults
#Effect
less
Detected-faults
#Software
detection
#Hardware
detection
Undetected-faults
#Incorrect
answer
#Loss
sequence
Original CMA
Hardened CMA
5000
10000
4072
(81.44%)
6021
(60.21%)
–
3979
(39.79%)
–
_
928
(18.56%)
_
–
_
3.2. Preliminary radiation testing campaign
To confirm the results gathered from fault injection experiments‚ we performed
a radiation test campaign. The radiation experiments consisted in exposing
only the processor to the charged particles issued from a Californium (Cf225)
source while executing both versions of the CMA program. Table 4-7 shows
the main features of the radiation experiments.
Table 4-7. Main characteristics for the radiation test campaign.
Program version
Flux
Estimated upsets
Exposure time
Original CMA
Hardened CMA
285
285
387
506
525
660