FXLS93421 datasheet(146/254 Pages) NXP

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NXP Semiconductors

FXLS9xxxx

Dual channel inertial sensor

11.9.3 Arming function: unfiltered mode

At the falling edge of SS_B for a sensor data SPI response for SOURCEID_0 (channel

0) or SOURCEID_2 (channel 1), the most recent available offset canceled sample for

the requested channel is compared against positive and negative thresholds that are

individually programmed for each channel via the CHx_ARM_T_x and CHx_ARM_T_x

registers. See Section 11.2.29 for register details. If the sample equals or exceeds either

threshold, an arming condition is indicated.

Once an arming condition is indicated for the associated channel, the arm pin output for

that channel is asserted when SS_B is asserted and the MISO data includes a sensor

data response for that channel. The pulse stretch function is not applied in Unfiltered

mode.

Figure 59 contains a block diagram of the Arming Function operation in Unfiltered Mode.

Figure 60 shows the Arming output operation under the different SPI request conditions.

ARMING FUNCTION

INTERPOLATED SAMPLE RATE

ARM_CFG[2]

SS_B

ch select

ARM_CFG[1]

aaa-030642

ARM

I/O

Figure 59. Arming function block diagram - unfiltered mode

aaa-030643

request SnsData

SCLK

ARM

tARM_UF_DLY

data latched for

arm function and SPI

MISO

MOSI

SS_B

SnsData resp

arming

condition

not present

request SnsData

SnsData resp

tARM_UF_ASSERT

request SnsData

SnsData resp

request SnsData

SnsData resp

arming

condition

not present

arming

condition

not present

arming

condition

present

Figure 60. Arming condition, unfiltered mode

11.9.4 Arming function down sampling

The data provided to the arming function can be down sampled using the ARM_DS[1:0]

bits in the CHx_ARM_CFG registers.

The initial value of the counter is zero. At the falling edge of SS_B for a sensor data

SPI response, if the counter value is equal to '00', the arming function is updated with

the new sample as described in Section 11.9.1 or Section 11.9.2. The counter is then

FXLS9xxxx

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Product data sheet

Rev. 6 — 8 February 2021

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