Embedded Software for SoC - Grupo de Mecatrônica EESC/USP

48 Chapter 4
Table 4-2. Experimental results – faults injected in the DSP32C registers.
Program version
#Injected
faults
#Effect
less
Detected-faults
#Software
detection
#Hardware
detection
Undetected-faults
#Incorrect
answer
#Loss
sequence
Original CMA 8000
7612
(95.15%)
-
88
(1.10%)
114
(1.43%)
186
(2.32%)
Hardened CMA 19520
18175
(93.11%)
1120
(5.74%)
193
(0.99%)
25
(0.13%)
7
(0.03%)
In order to compare both versions of the CMA program, the detection efficiency
and the error rate were calculated according to equations 4-1 and 4-2;
Table 4-3 summarizes the obtained figures.
As shown in Table 4-3, for the hardened CMA program were detected more
than 80% of the injected faults which modify the program’s behavior, while
the error rate was drastically reduced; a factor higher than 20.
Table 4-3. Detection efficiency and error rate for both program versions.
Detection efficiency
Error rate
CMA Original
none
3.75%
CMA Hardened
83.27%
0.16%
3.1.2. Fault injection in the program code
Results gathered from fault injection sessions when faults were injected in the
program code itself are shown in Table 4-4. The number of injected faults in
the program code was chosen as being proportional to the memory area
occupied by each tested program.
Table 4-5 illustrates the corresponding detection efficiency and error rate
calculated from results obtained when faults were injected in the program
Table 4-4. Experimental results – faults injected in the program code.
Program version
#Injected
faults
#Effect
less
Detected-faults
#Software
detection
#Hardware
detection
Undetected-faults
#Incorrect
answer
#Loss
sequence
Original CMA
2208
1422
(64.40%)
_
391
(17.71%)
217
(9.83%)
178
(8.06%)
Hardened CMA
8000
5038
(62.98%)
1658
(20.73%)
1210
(15.12%)
50
(0.62%)
44
(0.55%)