AN910 Datasheet, PDF (12/51 Pages) STMicroelectronics – ST7 AND ST9 PERFORMANCE BENCHMARKING

ST7 AND ST9 PERFORMANCE BENCHMARKING
Concerning code efficiency, the position of the ST9+ MCU is also among the best MCUs.
The 16-bit MCUs are only a little better, although favoured by their true 16-bit computing and
data manipulation instructions. In the 8/16-bit MCUs, the H8/300 takes a little advantage due
to its special block move instruction. But all 8-bit MCUs, even with shorter instruction lengths,
have longer code size results.
4.2.2 Interrupt processing performance results
Regarding speed, the ST9+ MCU ranks at the first position. The value chart shows that it
has the shortest interrupt latency but also an interrupt routine execution time which is
among the best. These results show that its interruption management and instruction cycle
time have been considerably enhanced. The register groups bring in addition fast context
switching capabilities.
Some 8-bit MCUs, such as the 68HC08, work quite well in this test. But their performance
must be moderated because such MCUs can manage only one interrupt at the time and so
cast off a complex arbitration phase. The interrupt management of the ST9+ is one of the
more advanced, allowing nested interrupts with full software programmable priorities
and program priority level control.
Code efficiency results for interrupt processing performance are not really significant. The
code represents only a very small part of an entire interrupt service routine, and so no
conclusion can be made.
4.2.3 Conclusion
Global results and all its characteristics allow the ST9+ to compete with the true 16-bit
MCUs on 8-bit and low-end 16-bit applications, and confirm its position of high-end 8/16-bit
MCU.
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