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16-BIT TIMING OPERATIONS USING ST7262 OR ST7263B MCUs

Figure 6. Frequency Measurement

In this example we will also use two 16-bit variables to hold the 16-bit timer value each time

an input capture occurs (StartPeriod: for the first rising edge and EndPeriod for the second

falling edge). In addition to these two variables, we will need an extra variable (FirstEdge)

which is used to indicate the first rising edge or the second edge.

– FisrtEdge =0: First Rising edge (PeriodStart)

– FisrtEdge =1: Second Rising edge (PeriodEnd)

In this case we will need only one input capture pin (ARTIC1) configured to detect only rising

edge.

The capture steps are shown in Figure 7. After selecting the timer frequency and the input

capture edge we wait for an input capture interrupt. Depending on the FirstEdge value the

input capture parameters (ICxR and the TBU) are transferred into PeriodStart or PeriodEnd.

Figure 7. Input Capture Sequence

Frequency= 1 / Period

input capture

No

YES

0

1

- Configure Time clock frequency

- Select sensitive edge on ICAP pins

- Cascade PWMART & TBU, FirstEdge = 0

- Store the TBU (compensated value)

in PeriodStartHR

- Store the ICxR in PeriodStartLR

- Store the TBU (compensated value)

in PeriodEndHR

- Store the ICxR Value in PeriodEndLR

First Edge =?