AN3393 datasheet(75/103 Pages) STMICROELECTRONICS

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AN3393

Peak detection

103

Peak detection

The purpose of this function is to memorize the absolute highest peak value reached by any

axis during the state machine execution and set the temporary axis mask (TMASK

described in Section 7.3) to follow the axis with the highest peak value.

The peak detection function is available both in State Machine 1 and in State Machine 2.

The two different absolute peak values are stored respectively in the PEAK1 (19h) and

PEAK2 (1Ah) registers. To enable peak detection, the P_DET bit in the SETTy register must

be set to 1.

Peak detection is a separate and optional function of the available opcode commands. In

order to find the peak value, this function always implements a “greater than” condition and

converts the measured value to an absolute number.

Figure 15 shows an example of peak detection.

Figure 15. Peak detection example

The example starts with the following settings:

–

MASK1 = F0h (+-x enabled, +-y enabled);

–

P_DET = 1 in the SETT1 register (Peak detection enabled on State Machine 1);

–

ABS = 0 in the SETT1 register (Unsigned threshold);

–

TMASK1 = 0 (Temporary mask default value).

In the first phase (State 1), the NEXT condition (GNTH1 in this case) is evaluated. Since the

positive Y-axis shows the absolute maximum value, the temporary mask (TMASK1)

contains +y and the absolute peak value is stored in the PEAK1 register.

AM14781V1

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