AN910 datasheet(12/51 Pages) STMICROELECTRONICS

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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.

AN910 データシート(PDF) 12 Page - STMicroelectronics