AN3393 datasheet(71/103 Pages) STMICROELECTRONICS

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AN3393

Axis mask filter

103

Note that at the first state of the state machine, the default mask (MASKy_A) is always

used.

For each axis, four different mask settings are possible:

Positive axis bit = 0 / Negative axis bit = 0, axis is then disabled.

Positive axis bit = 0 / Negative axis = 1, data of axis with opposite sign is then enabled

(e.g.: -Data < Threshold).

Positive axis bit = 1 / Negative axis = 0, data of axis with current sign is then enabled

(e.g.: Data < Threshold).

Positive axis bit = 1 / Negative axis = 1, data of axis with current sign and data of axis

with opposite sign are enabled ((e.g.: Data < Threshold, -Data < Threshold).

Table 87 shows the content of a MASKy register.

The order of axis mask evaluation is the following:

+X, -X, +Y, -Y, +Z, -Z, +V, -V.

Note that when the ABS bit in SETT1 (5Bh) / SETT2 (7Bh) register is set to zero, absolute

values are used for axis data and thresholds (e.g.: |Data| < |Threshold|).

7.2

Sign filter

The sign filter function is used to define whether the thresholds are signed (ABS bit set to 1

in the SETTy register) or unsigned (SETTy, bit ABS set to 0).

Figure 13 shows how the bit ABS in the SETTy register affects the thresholds.

Table 87. MASKy register

P_X

N_X

P_Y

N_Y

P_Z

N_Z

P_V

N_V

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