MMA65XX datasheet(39/56 Pages) FREESCALE

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Sensor

Freescale Semiconductor, Inc.

MMA65xx

3.8.10.3

Arming Function: Unfiltered Mode

On the rising edge of CS for an acceleration request, the most recent available offset cancelled sample for the requested axis

is compared against positive and negative thresholds that are individually programmed for each axis via the ARMT_Xx and

ARMT_Yx registers. Reference Section 3.1.10 for register details. If the sample equals or exceeds either threshold, an arming

condition is indicated.

Once an arming condition is indicated for the X-Axis, the ARM_X output is asserted when CS is asserted and the MISO data

includes an acceleration response for that axis.

Once an arming condition is indicated for the Y-Axis, the ARM_Y output is asserted when CS is asserted and the MISO data

includes an acceleration response for that axis.

The pulse stretch function is not applied in Unfiltered mode.

Figure 29 contains a block diagram of the Arming Function operation in Unfiltered Mode. Figure 30 shows the Arming output

operation under the different SPI request conditions.

Figure 29. Arming Function Block Diagram - Unfiltered Mode

Figure 30. X and Y Axis Arming Conditions, Unfiltered Mode

ARMING FUNCTION

ACFG[2]

AXIS Select

Interpolated Sample Rate

ARM_x

I/O

ACFG[1]

Y-Axis Arm Condition

Present

SCLK

MOSI

MISO

Request X-Axis

Request Y-Axis

X-Axis Response

Y-Axis Response

Request X-Axis

Request Y-Axis

X-Axis Response

ARM_X

ARM_Y

Y-Axis Response

Y-Axis Arm Condition

Not Present

X-Axis Arm Condition

Not Present

X-Axis Arm Condition

Present

tARM_UF_DLY

tARM_UF_ASSERT

tARM_UF_DLY

tARM_UF_ASSERT

X-Axis Data

Latched for

Arm & SPI

Y-Axis Data

Latched for

Arm & SPI

X-Axis Data

Latched for

Arm & SPI

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