AN910 datasheet(47/51 Pages) STMICROELECTRONICS

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ST7 AND ST9 PERFORMANCE BENCHMARKING

routine and so the start of the measure on the oscilloscope (trigger on positive edge). The

following lines are the implementation of the algorithm. This part ends with the reset of the I/O

pin and a return of the call.

The execution time is the length of the pulse triggered with the oscilloscope. Figure 8. shows

the diagram of the way of execution time measurement proceeding.

Note that it was sometimes not possible to implement all the tests on an MCU (see

<Italic>9.2.2 Memory considerations<Italic end>). In some of these cases, test routines have

even been written and execution time has been calculated theoretically. The theoretical

execution time is simply given by dividing the number of clock cycles, calculated the assembly

source, by the internal processing frequency:

Note that experience has shown the accuracy of these theoretical calculations in front of real

measures. Thus results of both types can be compared.

Figure 8. Execution time measurement proceeding

number of clock cycles

Theoretical execution time =

internal clock frequency

Oscilloscope screen

Test routine

pulse

Execution time

Assignments &

Initializations

.....

reset I/O pin

.....

Infinite Loop

Test Loop

set I/O pin

.....

reset I/O pin

AN910 Datasheet(PDF) 47 Page - STMicroelectronics