Technical Data Sheet - Freescale Semiconductor

Freescale Semiconductor
Data Sheet: Technical Data
Document Number: FXLS8471Q
Rev. 1.5, 06/2015
An Energy-Efficient Solution by Freescale
FXLS8471Q, 3-Axis,
Linear Accelerometer
FXLS8471Q
FXLS8471Q is a small, low-power, 3-axis, linear accelerometer in a
3 mm x 3 mm x 1 mm QFN package. FXLS8471Q has dynamically selectable
acceleration full-scale ranges of ±2 g/±4 g/±8 g and 14 bits of resolution.
Output data rates (ODR) are programmable from 1.563 Hz to 800 Hz. I2C and
SPI serial digital interfaces are provided along with several user
programmable event detection functions that can be used to reduce the overall
system power consumption by off-loading the host processor. FXLS8471Q is
guaranteed to operate over the extended temperature range of -40 °C to
+85 °C.
L
FX
Features
•
RST
N/C
VDD
Top View
16
15
14
VDDIO
1
13
Reserved
BYP
2
12
GND
Reserved
3
11
INT1
SCL/SCLK
4
10
SA1/CS_B
GND
5
9
INT2
FXLS8471Q
6
7
8
N/C
•
•
16 LEAD QFN
3 mm x 3 mm x 1 mm
SA0/MISO
•
1.95 V to 3.6 V VDD supply voltage, 1.62 V to 3.6 V VDDIO voltage
±2 g/±4 g/±8 g dynamically selectable acceleration full-scale ranges
Output Data Rates (ODR) from 1.563 Hz to 800 Hz
Low noise: typically 99 μg/Hz in low-noise mode @ 200-Hz bandwidth
14-bit ADC resolution: 0.244 mg/LSB in ±2 g, full-scale range
Embedded programmable acceleration event functions:
— Freefall and Motion Detection
— Transient Detection
— Vector-Magnitude Change Detection
— Pulse and Tap Detection (Single and Double)
— Orientation Detection (Portrait/Landscape)
Programmable automatic ODR change using Auto-Wake and return to
Sleep functions to save power.
192-byte FIFO buffer, capable of storing up to 32 samples of X/Y/Z data
Supports 4-wire SPI interface at up to 1 MHz; I2C Normal (100 kHz) and
Fast Modes (400 kHz)
Integrated accelerometer self-test function
SDA/MOSI
•
•
•
•
•
•
1Q
47
S8
Pin Connections
Target Markets
•
Industrial applications: vibration analysis, machine health monitoring, and platform stabilization
•
Smartphones, tablets, digital cameras, and personal navigation devices
•
Medical applications: patient monitoring, fall detection, and rehabilitation
Applications
•
•
•
•
•
Shock and vibration monitoring (mechatronic compensation, shipping, and warranty usage logging)
User interface (menu scrolling by orientation change, tap detection for button replacement)
Orientation detection (portrait/landscape: up/down, left/right, back/front position identification)
Gaming and real-time activity analysis (pedometry, freefall and drop detection for hard disk drives and other devices)
Power management for mobile devices using inertial event detection
Freescale reserves the right to change the detail specifications as may be required to permit
improvements in the design of its products.
© 2013-2015 Freescale Semiconductor, Inc. All rights reserved.
ORDERING INFORMATION
Part Number
Temperature Range
Package Description
Shipping
FXLS8471QR1
-40°C to +85°C
QFN-16
Tape and Reel (1 k)
Related Documentation
The FXLS8471Q device features and operations are described in a variety of reference manuals, user guides, and application
notes. To find the most-current versions of these documents:
1.
Go to the Freescale homepage at:
http://www.freescale.com/
2.
In the Keyword search box at the top of the page, enter the device number FXLS8471Q.
In the Refine Your Result pane on the left, click on the Documentation link.
FXLS8471Q
2
Sensors
Freescale Semiconductor, Inc.
Contents
1
2
Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3 Example FXLS8471Q Driver Code. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2 FXLS8471Q Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3 Sensor data structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.4 FXLS8471Q Configuration function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.5 FXLS8471Q Data Read function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2 Zero-g Offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.3 Self-Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5 Device Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.1 Mechanical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.3 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6 Digital Interfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1 I2C interface characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1.1
General I2C operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.1.2
I2C Read/Write operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.2 SPI Interface characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.2.1
General SPI operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.2.2
SPI READ/WRITE operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.2.3
I2C/SPI auto detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.2.4
Power supply sequencing and I2C/SPI mode auto-detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7 Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8 Embedded Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1 Factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.2 8-bit or 14-bit data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.3 Low-power modes versus high-resolution modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.4 Auto-Wake/Sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.5 Freefall and Motion event detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.5.1
Freefall detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.5.2
Motion detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.6 Transient detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.7 Pulse detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.8 Orientation detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.9 Acceleration Vector-Magnitude detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
9
Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
10 Registers by Functional Blocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.1 Device configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.1.1 STATUS (0x00) register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.1.2 DR_STATUS (0x00) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
10.1.3 F_STATUS (0x00) register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
10.1.4 TRIG_CFG (0x0A) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.1.5 SYSMOD (0x0B) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.1.6 INT_SOURCE (0x0C) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
10.1.7 WHO_AM_I (0x0D) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10.1.8 CTRL_REG1 (0x2A) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10.1.9 CTRL_REG2 (0x2B) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
10.1.10 CTRL_REG3 [Interrupt Control Register] (0x2C) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
10.1.11 CTRL_REG4 [Interrupt Enable Register] (0x2D) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
10.1.12 CTRL_REG5 [Interrupt Routing Configuration Register] (0x2E) register. . . . . . . . . . . . . . . . . . . . . . . . . . 37
10.2 Auto-Sleep trigger. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
10.2.1 ASLP_COUNT (0x29) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
10.3 Output data registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
10.3.1 OUT_X_MSB (0x01), OUT_X_LSB (0x02), OUT_Y_MSB (0x03), OUT_Y_LSB (0x04),
OUT_Z_MSB (0x05), OUT_Z_LSB (0x06) registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
10.4 FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
10.4.1 F_SETUP (0x09) register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
10.5 Sensor data configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
FXLS8471Q
Sensors
Freescale Semiconductor, Inc.
3
10.5.1 XYZ_DATA_CFG (0x0E) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
10.6 High-Pass filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
10.6.1 HP_FILTER_CUTOFF (0x0F) register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
10.7 Portrait/Landscape Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
10.7.1 PL_STATUS (0x10) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
10.7.2 PL_CFG (0x11) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
10.7.3 PL_COUNT (0x12) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
10.7.4 PL_BF_ZCOMP (0x13) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
10.7.5 PL_THS_REG (0x14) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
10.8 Freefall and Motion detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
10.8.1 A_FFMT_CFG (0x15) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
10.8.2 A_FFMT_SRC (0x16) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
10.8.3 A_FFMT_THS (0x17), A_FFMT_ THS_X_MSB (0x73), A_FFMT_THS_X_LSB (0x74),
A_FFMT_THS_Y_MSB (0x75), A_FFMT_THS_Y_LSB (0x76), A_FFMT_THS_Z_MSB (0x77),
A_FFMT_THS_Z_LSB (0x78) registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
10.8.4 A_FFMT_COUNT (0x18) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
10.9 Accelerometer vector-magnitude function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.9.1 A_VECM_CFG (0x5F) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
10.9.2 A_VECM_THS_MSB (0x60) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
10.9.3 A_VECM_THS_LSB (0x61) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
10.9.4 A_VECM_CNT (0x62) register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
10.9.5 A_VECM_INITX_MSB (0x63) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.9.6 A_VECM_INITX_LSB (0x64) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.9.7 A_VECM_INITY_MSB (0x65) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.9.8 A_VECM_INITY_LSB (0x66) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.9.9 A_VECM_INITZ_MSB (0x67) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
10.9.10 A_VECM_INITZ_LSB (0x68) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.10 Transient (AC) acceleration detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.10.1 TRANSIENT_CFG (0x1D) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.10.2 TRANSIENT_SRC (0x1E) register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
10.10.3 TRANSIENT_THS (0x1F) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.10.4 TRANSIENT_COUNT (0x20) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
10.11 Pulse detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
10.11.1 PULSE_CFG (0x21) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
10.11.2 PULSE_SRC (0x22) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
10.11.3 PULSE_THSX (0x23) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
10.11.4 PULSE_THSY (0x24) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
10.11.5 PULSE_THSZ (0x25) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
10.11.6 PULSE_TMLT (0x26) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
10.11.7 PULSE_LTCY (0x27) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
10.11.8 PULSE_WIND (0x28) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
10.12 Offset correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
10.12.1 OFF_X (0x2F) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
10.12.2 OFF_Y (0x30) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
10.12.3 OFF_Z (0x31) register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
11 Mounting Guidelines for the Quad Flat No-Lead (QFN) Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
11.1 Overview of soldering considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
11.2 Halogen content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
11.3 PCB mounting recommendations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
12 Package Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
13 Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
A.1 Errata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
A.1.1 SPI Mode Soft-reset using CTRL_REG2 (0x2B), bit 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
14 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
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Block Diagram
Figure 1. Block diagram
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RST
N/C
VDD
Pin Description
16
15
14
VDDIO
1
13
Reserved
BYP
2
12
GND
Reserved
3
11
INT1
SCL/SCLK
4
10
SA1/CS_B
GND
5
9
INT2
6
7
8
SA0/MISO
N/C
FXLS8471Q
SDA/MOSI
2
Top View
16 Lead QFN-COL
3 mm x 3 mm x 1 mm
Figure 2. Pinout diagram
Table 1. Pin Description
Pin
Name
1
VDDIO
Function
Interface power supply
2
BYP
3
Reserved
Test reserved, connect to GND
Internal regulator output bypass capacitor connection
4
SCL/SCLK
I2C Serial Clock/SPI Clock
5
GND
6
SDA/MOSI
Ground
7
SA0/MISO(1)
8
N/C
Internally not connected
9
INT2
Interrupt 2
10
SA1/CS_B
11
INT1
I2C Serial Data/SPI Master Out, Slave In
I2C address selection bit 0/SPI Master In, Slave Out
I2C address selection bit 1(2)/SPI Chip Select (active low)
Interrupt 1
12
GND
13
Reserved
Ground
14
VDD
Power supply
15
N/C
Internally not connected
16
RST
Reset input, active high. Connect to GND if unused
Test reserved, connect to GND
1. The SA0 pin is also used to select the desired serial interface mode during POR and also after a hard/soft reset event. Please see
Section 6.2.3, “I2C/SPI auto detection” for more information
2. See Table 8 for I2C address options selectable using the SA0 and SA1 pins.
Device power is supplied through the VDD pin. Power-supply, decoupling capacitors (100 nF ceramic plus 4.7 μF or larger bulk)
should be placed as close as possible to pin 14 of the device. The digital interface supply voltage (VDDIO) must also be
decoupled with a 100 nF ceramic capacitor placed as close as possible to pin 1 of the device.
The digital control signals SCL, SDA, SA0, SA1, and RST are not tolerant of voltages more than VDDIO + 0.3 V. If VDDIO is
removed, these pins will clamp any logic signals through their internal ESD protection diodes.
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The function and timing of the two interrupt pins (INT1 and INT2) are user-programmable through the I2C/SPI interface. The SDA
and SCL I2C connections are open drain and therefore require a pullup resistor as shown in the application diagram in Figure 3.
The INT1 and INT2 pins may also be configured for open-drain operation. If they are configured for open drain, external pullup
resistors are required.
RST
(Connect to GND if unused)
16
15
VDD
N/C
RST
VDD
0.1 μF
14
VDDIO
VDDIO
0.1 μF
BYP
0.1 μF
Reserved
SCL/SCLK
Reserved
1
13
2
12
3
FXLS8471Q
11
GND
4
10
5
9
VDDIO
8
INT2
INT1
VDDIO
INT2
Note: Pullup resistors on INT1 and INT2 are not required if these
pins are configured for push/pull (default) operation.
N/C
7
SA0/MISO
SCL/SCLK
SDA/MOSI
6
VDDIO
INT1
SA1/CS_B
GND
VDDIO
4.7 μF
SDA/MOSI
SA0/MISO
Note: Pullup resistors on SCL/SCLK and SDA/MOSI are not
required if the device is operated in SPI Interface mode.
Figure 3. Electrical connection
2.1
Soldering information
The QFN package is compliant with the RoHS standards. Please refer to Freescale application note AN4077 for more
information.
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2.2
Orientation
Top view
Side view
BOTTOM
Pin 1
Xout @ 0g
Yout @ 0g
Zout @ -1g
Xout @ 0g
Yout @ -1g
Zout @ 0g
TOP
Earth Gravity
Xout @ 0g
Yout @ 0g
Zout @ 1g
Xout @ -1g
Yout @ 0g
Zout @ 0g
Xout @ 1g
Yout @ 0g
Zout @ 0g
+Z
+X
1
Xout @ 0g
Yout @ 1g
Zout @ 0g
+Y
Top view
Figure 4. Component axes orientation and response to gravity stimulus
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Example FXLS8471Q Driver Code
3.1
Introduction
It is very straightforward to configure the FXLS8471Q and start receiving data from the three accelerometerchannels.
Unfortunately, since every hardware platform will be different, it is not possible to provide completely portable software drivers.
This section therefore provides real FXLS8471Q driver code for a Kinetis uC board running under the MQX operating system.
The I2C functions s_i2c_read_regs and s_i2c_write_regs are not provided here and should be replaced with the corresponding
low level I2C driver code on the development platform.
3.2
FXLS8471Q Addresses
This section lists the I2C address of the FXLS8471Q. The I2C address depends on the logic level of FXLS8471Q pins SA0 and
SA1 so the I2C address may be 0x1C, 0x1D, 0x1E or 0x1F.
Example 1.
// FXLS8471Q I2C address
#define FXLS8471Q_SLAVE_ADDR
0x1E
// with pins SA0=0, SA1=0
Some of the key FXLS8471Q internal register addresses are listed below.
Example 2.
// FXLS8471Q internal register addresses
#define FXLS8471Q_STATUS
0x00
#define FXLS8471Q_WHOAMI
0x0D
#define FXLS8471Q_XYZ_DATA_CFG
0x0E
#define FXLS8471Q_CTRL_REG1
0x2A
#define FXLS8471Q_WHOAMI_VAL
0x6A
The reference driver here does a block read of the FXLS8471Q status byte plus three 16-bit accelerometer channels.
Example 3.
// number of bytes to be read from FXLS8471Q
#define FXLS8471Q_READ_LEN 7// status plus 3 accelerometer channels
3.3
Sensor data structure
The high and low bytes of the three accelerometer are placed into a structure of type SRAWDATA containing three signed short
integers.
Example 4.
typedef struct
{
int16_t x;
int16_t y;
int16_t z;
} SRAWDATA;
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3.4
FXLS8471Q Configuration function
This function configures the FXLS8471Q for a 200-Hz ODR. The code is self-explanatory and can be easily customized for
different settings.
Example 5.
// function configures FXLS8471Q accelerometer sensor
static _mqx_int s_FXLS8471Q_start(MQX_FILE_PTR aFP)
{
uint8_t databyte;
// read and check the FXLS8471Q WHOAMI register
if (s_i2c_read_regs(aFP, FXLS8471Q_SLAVE_ADDR, FXLS8471Q_WHOAMI, &databyte,
(uint8_t) 1) != 1)
{
return (I2C_ERROR);
}
if (databyte != FXLS8471Q_WHOAMI_VAL)
{
return (I2C_ERROR);
}
// write 0000 0000 = 0x00 to accelerometer control register 1 to place FXLS8471Q into
// standby
// [7-1] = 0000 000
// [0]: active=0
databyte = 0x00;
if (s_i2c_write_regs(aFP, FXLS8471Q_SLAVE_ADDR, FXLS8471Q_CTRL_REG1, &databyte,
(uint8_t) 1) != 1)
{
return (I2C_ERROR);
}
// write 0000 0001= 0x01 to XYZ_DATA_CFG register
// [7]: reserved
// [6]: reserved
// [5]: reserved
// [4]: hpf_out=0
// [3]: reserved
// [2]: reserved
// [1-0]: fs=01 for accelerometer range of +/-4g with 0.488mg/LSB
databyte = 0x01;
if (s_i2c_write_regs(aFP, FXLS8471Q_SLAVE_ADDR, FXLS8471Q_XYZ_DATA_CFG,
&databyte, (uint8_t) 1) != 1)
{
return (I2C_ERROR);
}
// write 0001 0101b = 0x15 to accelerometer control register 1
// [7-6]: aslp_rate=00
// [5-3]: dr=010 for 200Hz data rate
// [2]: lnoise=1 for low noise mode
// [1]: f_read=0 for normal 16 bit reads
// [0]: active=1 to take the part out of standby and enable sampling
databyte = 0x15;
if (s_i2c_write_regs(aFP, FXLS8471Q_SLAVE_ADDR, FXLS8471Q_CTRL_REG1, &databyte,
(uint8_t) 1) != 1)
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{
return (I2C_ERROR);
}
// normal return
return (I2C_OK);
}
3.5
FXLS8471Q Data Read function
This function performs a block read of the status and acceleration data and places the bytes read into the structures of type
SRAWDATA as signed short integers.
Example 6.
// read status and the three channels of accelerometer data from
// FXLS8471Q (7 bytes)
int16_t ReadAccel(SRAWDATA *pAccelData)
{
MQX_FILE_PTR fp;
// I2C file pointer
uint8_t Buffer[FXLS8471Q_READ_LEN];
// read buffer
// read FXLS8471Q_READ_LEN=7 bytes (status byte and the three channels of data)
if (s_i2c_read_regs(fp, FXLS8471Q_SLAVE_ADDR, FXLS8471Q_STATUS, Buffer,
FXLS8471Q_READ_LEN) == FXLS8471Q_READ_LEN)
{
// copy the 14 bit accelerometer byte data into 16 bit words
pAccelData->x = ((Buffer[1] << 8) | Buffer[2])>> 2;
pAccelData->y = ((Buffer[3] << 8) | Buffer[4])>> 2;
pAccelData->z = ((Buffer[5] << 8) | Buffer[6])>> 2;
}
else
{
// return with error
return (I2C_ERROR);
}
// normal return
return (I2C_OK);
}
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4
Terminology
4.1
Sensitivity
The sensitivity is represented in LSB/g. In 2-g mode the sensitivity is 4096 LSB/g. In 4-g mode the sensitivity is 2048 LSB/ g and
in 8-g mode the sensitivity is 1024 LSB/g.
4.2
Zero-g Offset
Zero-g Offset describes the deviation of an actual output signal from the ideal output signal if the sensor is stationary. A sensor
stationary on a horizontal surface will measure 0 g in X-axis and 0 g in Y-axis whereas the Z-axis will measure 1 g. A deviation from
ideal value in this case is called Zero-g offset. Offset is to some extent a result of stress on the MEMS sensor and therefore the
offset can slightly change after mounting the sensor onto a printed circuit board or exposing it to extensive mechanical stress.
4.3
Self-Test
Self-Test can be used to verify the transducer functionality without applying an external mechanical stimulus. When Self-Test is
activated, an electrostatic actuation force is applied to the sensor, simulating a small acceleration. In this case, the sensor outputs
will exhibit a change in their DC levels which are related to the selected full scale through the device sensitivity. When Self-Test is
activated, the device output level is given by the algebraic sum of the signals produced by the acceleration acting on the sensor
and by the electrostatic self-test force.
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Device Characteristics
5.1
Mechanical characteristics
Table 2. Mechanical characteristics @ VDD = 2.5 V, VDDIO = 1.8 V T = 25°C unless otherwise noted.
Parameter
Test Conditions
Symbol
Min
Measurement range(1)
±4 g mode
SENACC
±4 g mode
±8 g mode
Sensitivity change with temperature
Sensitivity accuracy
Unit
g
±8
±2 g mode
(1)
Max
±4
FSACC
±8 g mode
Sensitivity
Typ
±2
±2 g mode
4096
LSB/g
0.244
mg/LSB
2048
LSB/g
0.488
mg/LSB
1024
LSB/g
0.976
mg/LSB
±2 g, ±4 g, ±8 g modes
TCSACC
±0.01
%/°C
@ 25°C
SEN-TOLACC
±2.5
%SENACC
Zero-g level offset accuracy(2)
±2 g, ±4 g, ±8 g modes
OFFACC
±20
mg
Zero-g level offset accuracy post-board mount(3)
±2 g, ±4 g, ±8 g modes
OFF-PBMACC
±30
mg
Zero-g level change versus temperature
Nonlinearity (deviation from straight line)(4)(5)
Self-Test output change(6)
X
Y
Z
Output noise density(4)(7)
Operating temperature range
1.
2.
3.
4.
5.
6.
7.
(1)
TCOACC
±0.2
mg/°C
Over ±1 g range normal mode
NLACC
±0.5
%FSACC
Set to ±2 g mode
STOCACC
-40°C to 85°C
ODR = 400 Hz, normal mode
ODR = 400 Hz, low-noise mode
(1)
+192
+270
+1275
126
NDACC-NM
NDACC-LNM
Top
LSB
µg/√Hz
99
-40
µg/√Hz
+85
°C
Dynamic range is limited to ±4 g when in the low-noise mode.
Before board mount.
Post-board mount offset specifications are based on a 2-layer PCB design.
Evaluation only.
After post-board mount corrections for sensitivity, cross axis and offset. Refer to AN4399 for more information.
Self-test is only exercised along one direction for each sensitive axis.
Measured using earth's gravitational field (1 g) with the device oriented horizontally (+Z axis up) and stationary.
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5.2
Electrical characteristics
Table 3. Electrical characteristics @ VDD = 2.5 V, VDDIO = 1.8 V T = 25°C unless otherwise noted.
Parameter
Test Conditions
Supply voltage
Interface supply voltage
Symbol
Min
Typ
Max
Unit
VDD
1.95
2.5
3.6
V
VDDIO
1.62
1.8
3.6
V
ODR = 12.5 Hz
Low-power acceleration mode
ODR = 100 Hz
8
IddACC-LPM
35
ODR = 400 Hz
ODR = 50 Hz
Normal acceleration mode
ODR = 200 Hz
35
IddACC-NM
130
ODR = 800 Hz
Current during boot sequence, 0.9 mS max duration
using recommended regulator bypass capacitor
µA
130
µA
240
VDD = 2.5 V
IddBOOT
Value of capacitor on BYP pin
-40°C to 85°C
CBYP
Standby mode current @ 25°C
Standby mode
IddSTBY
Standby mode current over-temperature range
Standby mode
IddSTBY
Digital high-level input voltage RST pin
VIHRST
Digital low-level input voltage RST pin
VILRST
Digital high-level input voltage
SCL, SDA, SA0, SA1
VIH
Digital low-level input voltage
SCL, SDA, SA0, SA1
VIL
75
100
3
mA
470
nF
10
µA
2
µA
1.04
V
0.68
0.75*VDDIO
V
V
0.3*VDDIO
V
High-level output voltage
INT1, INT2
IO = 500 µA
VOH
Low-level output voltage
INT1, INT2
IO = 500 µA
VOL
0.1*VDDIO
V
Low-level output voltage
SDA
IO = 500 µA
VOLSDA
0.1*VDDIO
V
SCL, SDA pin leakage
0.9*VDDIO
V
25°C
1.0
-40°C to 85°C
4.0
SCL, SDA pin capacitance
nA
3
VDD rise time
0.001
Boot time(1)
TBOOT
pf
1000
ms
1000
µs
(2)
TPOR→ACT
2/ODR + 2
ms
Turn-on time 2(3)
TSTBY→ACT
2/ODR + 1
ms
Turn-on time 1
Operating temperature range
TOP
-40
+85
°C
2
1. Time from VDDIO on and VDD > VDD min until I C/SPI interface ready for operation.
2. Time to obtain valid data from power-down mode to Active mode.
3. Time to obtain valid data from Standby mode to Active mode.
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5.3
Absolute maximum ratings
Stresses above those listed as “absolute maximum ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device under these conditions is not implied. Exposure to maximum rating conditions for
extended periods may affect device reliability.
Table 5. Maximum ratings
Rating
Maximum acceleration (all axes, 100 μs)
Supply voltage, IO voltage
Symbol
Value
Unit
gmax
5,000
g
VDDmax/
VDDIOmax
-0.3 to +3.6
V
VINmax
-0.3 to VDDIO + 0.3
V
Drop-Test height
Ddrop
1.8
m
Storage temperature range
TSTG
-40 to +125
°C
Symbol
Value
Unit
Human Body Model
HBM
±2000
V
Machine Model
MM
±200
V
Input voltage on any control pin (SA0/MISO, SA1/CS_B, SCL/SCLK, SDA/MOSI, RST)
Table 6. ESD and latchup protection characteristics
Rating
Charge Device Model
Latchup current at T = 85°C
CDM
±500
V
ILU
±100
mA
This device is sensitive to mechanical shock. Improper handling can cause permanent damage to the part or
cause the part to otherwise fail.
This device is sensitive to ESD, improper handling can cause permanent damage to the part.
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6
Digital Interfaces
6.1
I2C interface characteristics
Table 7. I2C slave timing values(1)
Parameter
I2C Fast Mode
Symbol
Unit
Min
Max
400
SCL Clock Frequency
fSCL
0
Bus Free Time between STOP and START condition
tBUF
1.3
μs
(Repeated) START Hold Time
tHD;STA
0.6
μs
(Repeated) START Setup Time
tSU;STA
0.6
μs
STOP Condition Setup Time
tSU;STO
0.6
SDA Data Hold Time
SDA Valid
SDA Valid Acknowledge Time
(4)
μs
(2)
μs
tVD;DAT
0.9(2)
μs
tVD;ACK
0.9(2)
μs
0.05
tHD;DAT
Time(3)
kHz
0.9
tSU;DAT
100
ns
SCL Clock Low Time
tLOW
1.3
μs
SCL Clock High Time
tHIGH
0.6
SDA Setup Time
μs
(5)
SDA and SCL Rise Time
tr
20 + 0.1 Cb
300
ns
SDA and SCL Fall Time
tf
20 + 0.1 Cb(5)
300
ns
tSP
0
50
ns
Pulse width of spikes on SDA and SCL that must be suppressed by
internal input filter
1.
2.
3.
4.
5.
All values referred to VIH (min) and VIL (max) levels.
This device does not stretch the LOW period (tLOW) of the SCL signal.
tVD;DAT = time for Data signal from SCL LOW to SDA output.
tVD;ACK = time for Acknowledgement signal from SCL LOW to SDA output (HIGH or LOW, depending on which one is worse).
Cb = total capacitance of one bus line in pF.
handbook, full pagewidth
SDA
tLOW
tf
tr
tSU;DAT
tf
tHD;STA
tSP
tr
tBUF
SCL
S
tHD;STA
tHD;DAT
tHIGH
tSU;STA
Sr
tSU;STO
P
S
MSC610
Figure 5. I2C slave timing diagram
FXLS8471Q
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6.1.1
General I2C operation
There are two signals associated with the I2C bus: the Serial Clock Line (SCL) and the Serial Data line (SDA). The latter is a
bidirectional line used for sending and receiving the data to/from the interface. External pullup resistors connected to VDDIO are
required for SDA and SCL. When the bus is free both the lines are high. The I2C interface is compliant with fast mode (400 kHz),
and normal mode (100 kHz) I2C standards. Operation at frequencies higher than 400 kHz is possible, but depends on several
factors including the pullup resistor values, and total bus capacitance (trace + device capacitance). See Table 8 for more
information.
A transaction on the bus is started through a start condition (ST) signal, which is defined as a HIGH-to-LOW transition on the
data line while the SCL line is held HIGH. After the ST signal has been transmitted by the master, the bus is considered busy.
The next byte of data transmitted contains the slave address in the first seven bits, and the eighth bit, the read/write bit, indicates
whether the master is receiving data from the slave or transmitting data to the slave. When an address is sent, each device in
the system compares the first seven bits after the ST condition with its own address. If they match, the device considers itself
addressed by the master. The 9th clock pulse, following the slave address byte (and each subsequent byte) is the acknowledge
(ACK). The transmitter must release the SDA line during the ACK period. The receiver must then pull the data line low so that it
remains stable low during the high period of the acknowledge clock period.
The number of bytes per transfer is unlimited. If a receiver can't receive another complete byte of data until it has performed some
other function, it can hold the clock line, SCL low to force the transmitter into a wait state. Data transfer only continues when the
receiver is ready for another byte and releases the data line. This delay action is called clock stretching. Not all receiver devices
support clock stretching. Not all master devices recognize clock stretching. This part does not use clock stretching.
A low to high transition on the SDA line while the SCL line is high is defined as a stop condition (SP) signal. A write or burst write
is always terminated by the master issuing the SP signal. A master should properly terminate a read by not acknowledging a byte
at the appropriate time in the protocol. A master may also issue a repeated start signal (SR) during a transfer
The slave addresses that may be assigned to the FXLS8471Q part are 0x1C, 0x1D, 0x1E, or 0x1F. The selection is made through
the logic level of the SA1 and SA0 inputs.
Table 8. I2C slave address
6.1.2
SA1
SA0
0
0
Slave address
0x1E
0
1
0x1D
1
0
0x1C
1
1
0x1F
I2C Read/Write operations
Single-byte read
The master (or MCU) transmits a start condition (ST) to the FXLS8471Q, followed by the slave address, with the R/W bit set to
“0” for a write, and the FXLS8471Q sends an acknowledgement. Then the master (or MCU) transmits the address of the register
to read and the FXLS8471Q sends an acknowledgement. The master (or MCU) transmits a repeated start condition (SR), followed
by the slave address with the R/W bit set to “1” for a read from the previously selected register. The FXLS8471Q then
acknowledges and transmits the data from the requested register. The master does not acknowledge (NAK) the transmitted data,
but transmits a stop condition to end the data transfer.
Multiple-byte read
When performing a multi-byte or “burst” read, the FXLS8471Q automatically increments the register address read pointer after
a read command is received. Therefore, after following the steps of a single-byte read, multiple bytes of data can be read from
sequential registers after each FXLS8471Q acknowledgment (AK) is received until a no acknowledge (NAK) occurs from the
master followed by a stop condition (SP) signaling an end of transmission.
Single-byte write
To start a write command, the master transmits a start condition (ST) to the FXLS8471Q, followed by the slave address with the R/
W bit set to “0” for a write, and the FXLS8471Q sends an acknowledgement. Then the master (or MCU) transmits the address of
the register to write to, and the FXLS8471Q sends an acknowledgement. Then the master (or MCU) transmits the 8-bit data to
write to the designated register and the FXLS8471Q sends an acknowledgement that it has received the data. Since this
transmission is complete, the master transmits a stop condition (SP) to end the data transfer. The data sent to the FXLS8471Q
is now stored in the appropriate register.
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Multiple-byte write
The FXLS8471Q automatically increments the register address write pointer after a write command is received. Therefore, after
following the steps of a single-byte write, multiple bytes of data can be written to sequential registers after each FXLS8471Q
acknowledgment (ACK) is received.
< Single-byte Read >
Master
ST
Device Address[6:0]
W
Register Address[7:0]
AK
Slave
SR
Device Address[6:0]
R
AK
NAK SP
AK
Data[7:0]
< Multiple-byte Read >
Master
ST
Device Address[6:0]
W
Register Address[7:0]
AK
Slave
AK
Master
Data[7:0]
R
AK
AK
Data[7:0]
Slave
SR Device Address[6:0]
AK
AK
NAK
Data[7:0]
SP
Data[7:0]
< Multiple-byte Write >
Master
ST
Device Address[6:0]
W
Register Address[7:0]
AK
Slave
Data[7:0]
AK
Data[7:0]
AK
SP
AK
< Single-byte Write >
Master
ST
Device Address[6:0]
Slave
W
Register Address[7:0]
AK
Data[7:0]
AK
SP
AK
Legend
ST: Start Condition
SR: Repeated Start Condition
SP: Stop Condition
AK: Acknowledge
NAK: No Acknowledge
R: Read = 1
W: Write = 0
Figure 6. I2C timing diagram
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6.2
SPI Interface characteristics
SPI interface is a classical master/slave serial port. The FXLS8471Q is always considered as the slave and thus is never initiating
the communication.
Table 9 and Figure 7 describe the timing requirements for the SPI system.
Table 9. SPI timing
Function
Symbol
Min
Max
Unit
Of
—
1
MHz
SCLK Period
tSCLK
1000
—
ns
SCLK High time
tCLKH
500
—
ns
SCLK Low time
tCLKL
500
—
ns
CS_B lead time
tSCS
65
—
ns
CS_B lag time
tHCS
65
—
ns
MOSI data setup time
tSET
25
—
ns
MOSI data hold time
tHOLD
75
—
ns
MISO data valid (after SCLK low edge)
tDDLY
—
500
ns
Width CS High
tWCS
100
—
ns
Operating Frequency
CS_B
SCLK
MOSI
MISO
Figure 7. SPI Timing Diagram
6.2.1
General SPI operation
The CS_B pin is driven low at the start of a SPI transaction, held low for the duration of the transaction, and driven high after the
transaction is complete. During a transaction the master toggles the SPI clock (SCLK) and transmits data on the MOSI pin.
A write operation is initiated by transmitting a 1 for the R/W bit. Then the 8-bit register address, ADDR[7:0] is encoded in the first
and second serialized bytes. Data to be written starts in the third serialized byte. The order of the bits is as follows:
Byte 0: R/W,ADDR[6],ADDR[5],ADDR[4],ADDR[3],ADDR[2],ADDR[1],ADDR[0],
Byte 1: ADDR[7],X,X,X,X,X,X,X,
Byte 2: DATA[7],DATA[6],DATA[5],DATA[4],DATA[3],DATA[2],DATA[1],DATA[0].
Multiple bytes of DATA may be transmitted. The X indicates a bit that is ignored by the part. The register address is autoincremented so that the next clock edges will latch the data for the next register. When desired, the rising edge on CS_B stops
the SPI communication.
The FXLS8471Q SPI configuration is as follows:
•
•
•
Polarity: rising/falling
Phase: sample/setup
Order: MSB first
Data is sampled during the rising edge of SCLK and set up during the falling edge of SCLK.
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6.2.2
SPI READ/WRITE operations
A READ operation is initiated by transmitting a 0 for the R/W bit. Then the 8-bit register address, ADDR[7:0] is encoded in the
first and second serialized bytes. Subsequent bits are ignored by the part. The read data is deserialized from the MISO pin.
Similarly a WRITE operation is initiated by transmitting a 1 for the R/W bit. After the first and second serialized bytes multipledata bytes can be transmitted into consecutive registers, starting from the indicated register address in ADDR[7:0].
An SPI transaction is started by asserting the CS_B pin (high-to-low transition), and ended by deasserting the CS_B pin (low-tohigh transition).
R/W bit followed by ADDR [6:0] ADDR[7] followed by 7 “don’t care” bits
Data0*
Data1
—
Datan
* Data bytes must be transmitted to the slave (FXLS8471Q) using the MOSI pin by the master when R/W = 1. Data bytes will be transmitted by
the slave (FXLS8471Q) to the master using the MISO pin when R/W = 0. The first 2 bytes are always transmitted by the master using the MOSI
pin. That is, a transaction is always initiated by master. 1
Figure 8. SPI single-burst READ/WRITE transaction diagram
The registers embedded inside FXLS8471Q are accessed through either an I2C, or a SPI serial interface. To enable either
interface the VDDIO line must be connected to the interface supply voltage. If VDD is not present and VDDIO is present
FXLS8471Q is in shutdown mode and communications on the interface are ignored. If VDDIO is held high, VDD can be powered
off and the communications pins will be in a high impedance state. This will allow communications to continue on the bus with
other devices.
Table 10. Serial interface pin descriptions
Pin Name
VDDIO
6.2.3
Pin Description
Digital interface power
SA1/CS_B
I2C second least significant bit of device address/SPI chip select
SCL/SCLK
I2C/SPI serial clock
SDA/MOSI
I2C serial data/SPI master serial data out slave serial data in
SA0/MISO
I2C least significant bit of the device address/SPI master serial data in slave out
I2C/SPI auto detection
Table 11. I2C/SPI auto detection
SA0
Slave address
GND
I 2C
VDDIO
I2C
Floating
SPI
FXLS8471Q employs an interface mode, auto-detection circuit that will select either I2C or SPI interface mode based on the state
of the SA0 pin during power up or when exiting reset. Once set for I2C or SPI operation, the device will remain in I2C or SPI mode
until the device is reset or powered down and the auto-detection process is repeated. Please note that when SPI interface mode
is desired, care must be taken to ensure that no other slave device drives the common SA0/MISO pin during the 1 ms period
after a hard or soft reset or powerup event.
6.2.4
Power supply sequencing and I2C/SPI mode auto-detection
FXLS8471Q does not have any specific power supply sequencing requirements between VDD and VDDIO voltage supplies to
ensure normal operation. To ensure correct operation of the I2C/SPI auto-detection function, VDDIO should be applied before or
at the same time as VDD. If this order cannot be maintained, the user should either toggle the RST line or power cycle the VDD
rail in order to force the auto-detect function to restart and correctly identify the desired interface. FXLS8471Q will indicate
completion of the reset sequence by toggling the INT1 pin from logic high to low to high over a 500 ns period. If the INT1 pin was
already low prior to the reset event, it will only go high.
FXLS8471Q
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7
Modes of Operation
Sleep
Active
OFF
Standby
Wake
Figure 9. FXLS8471Q power mode transition diagram
Table 12. Mode of operation description
Mode
OFF
I2C/SPI Bus state
Powered down
VDD
VDDIO
<1.8 V VDDIO can be > VDD
Function description
The device is powered off. All analog and digital blocks
are shutdown. I2C bus inhibited.
Standby
I2C/SPI communication with
FXLS8471Q is possible
ON
VDDIO = High
VDD = High
Active bit is cleared
Only digital blocks are enabled.
Analog subsystem is disabled. Internal clocks disabled.
Active
(Wake/Sleep)
I2C/SPI communication with
FXLS8471Q is possible
ON
VDDIO = High
VDD = High
Active bit is set
All blocks are enabled (digital and analog).
All register contents are preserved when transitioning from Active to Standby mode, but some registers are reset when
transitioning from Standby to Active. These registers are noted in Table 13, “Register Address Map,” on page 25. The Sleep and
Wake modes are active modes. For more information on how to use the Sleep and Wake modes and configuring the device to
transition between them, please refer to Section 8, “Embedded Functionality” or Freescale application note AN4074.
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8
Embedded Functionality
FXLS8471Q is a low-power, digital output 3-axis acceleration sensor with both I2C and SPI interface options. Extensive
embedded functionality is provided to detect inertial events at low power, with the ability to notify the host processor via either of
the two programmable interrupt pins. The embedded functionality includes:
•
•
•
•
•
•
•
•
•
8-bit or 14-bit accelerometer data with an option for high-pass filtered output data
Four different oversampling options for the output data. The oversampling settings allow the end user to optimize the
resolution versus power consumption trade-off in a given application.
A low-noise accelerometer mode that functions independently of the oversampling modes for even higher resolution
Low-power auto-wake/sleep function for conserving power in portable battery powered applications
Accelerometer pulse detection circuit which can be used to detect directional single and double taps
Accelerometer directional motion and freefall event detection with programmable threshold and debounce time
Acceleration transient detection with programmable threshold and debounce time. Transient detection can employ either
a high-pass filter or use the difference between reference and current sample values.
Orientation detection with programmable hysteresis for smooth transitions between portrait and landscape orientations
Accelerometer vector-magnitude change event detection with programmable reference, threshold, and debounce time
values
Many different configurations of the above functions are possible to suit the needs of the end application. Separate application
notes are available to further explain the different configuration settings and potential use cases.
8.1
Factory calibration
FXLS8471Q is factory calibrated for sensitivity and offset on each axis. The trim values are stored in Non-Volatile Memory (NVM).
On startup, the trim parameters are read from NVM and applied to the internal compensation circuitry. After mounting the device
to the PCB, the user may further adjust the accelerometer offsets through the OFF_X/Y/Z registers. For more information on
accelerometer calibration, refer to Freescale application note AN4069.
8.2
8-bit or 14-bit data
The measured acceleration data is stored in the OUT_X_MSB, OUT_X_LSB, OUT_Y_MSB, OUT_Y_LSB, OUT_Z_MSB, and
OUT_Z_LSB registers as 2’s complement 14-bit numbers. The most significant 8-bits of each axis are stored in the OUT_X, Y,
Z_MSB registers, so applications needing only 8-bit results simply read these three registers and ignore the OUT_X,Y, Z_LSB
registers. To do this, the f_read mode bit in CTRL_REG1 must be set.
When the full-scale range is set to 2 g, the measurement range is -2 g to +1.999 g, and each count corresponds to 0.244 mg at
±14-bits resolution. When the full-scale is set to 8 g, the measurement range is -8 g to +7.996 g, and each count corresponds to
0.976 mg. The resolution is reduced by a factor of 64 if only the 8-bit results are used (CTRL_REG1[f_read] = 1). For further
information on the different data formats and modes, please refer to Freescale application note AN4076.
8.3
Low-power modes versus high-resolution modes
FXLS8471Q can be optimized for lower power or higher resolution of the accelerometer output data. High resolution is achieved
by setting the lnoise bit in register 0x2A. This improves the resolution (by lowering the noise), but be aware that the dynamic
range becomes fixed at ±4 g when this bit is set. This will affect all internal embedded functions (scaling of thresholds, etc.) and
reduce noise. Another method for improving the resolution of the data is through oversampling. One of the oversampling
schemes of the output data can be activated when CTRL_REG2[mods] = 2’b10 which will improve the resolution of the output
data without affecting the internal embedded functions or fixing the dynamic range.
There is a trade-off between low power and high resolution. Low power can be achieved when the oversampling rate is reduced.
When CTRL_REG2[mods] = 2’b10, the lowest power is achieved, at the expense of higher noise. In general, the lower the
selected ODR and OSR, the lower the power consumption. For more information on how to configure the device in low-power or
high-resolution modes and understand the benefits and trade-offs, please refer to Freescale application note AN4075.
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8.4
Auto-Wake/Sleep mode
FXLS8471Q can be configured to transition between sample rates (with their respective current consumptions) based on the
status of the embedded interrupt event generators in the device. The advantage of using the Auto-Wake/Sleep is that the system
can automatically transition to a higher sample rate (higher current consumption) when needed but spends the majority of the
time in the Sleep mode (lower current) when the device does not require higher sampling rates. Auto-Wake refers to the device
being triggered by one of the interrupt event functions to transition to a higher sample rate. This may also interrupt the processor
to transition from a sleep mode to a higher power mode.
Sleep mode occurs when none of the enabled interrupt event functions has detected an interrupt within the user-defined, timeout period. The device will then transition to the specified lower sample rate. It may also alert the processor to go into a lower power
mode to save power during this period of inactivity. Please refer to AN4074 for more detailed information on configuring the AutoWake/Sleep function.
8.5
Freefall and Motion event detection
FXLS8471Q integrates a programmable threshold based acceleration detection function capable of detecting either motion or
freefall events depending upon the configuration. For further details and examples on using the embedded freefall and motion
detection functions, please refer to Freescale application note AN4070.
8.5.1
Freefall detection
The detection of “Freefall” involves the monitoring of the X, Y, and Z axes for the condition where the acceleration magnitude is
below a user-specified threshold for a user-definable amount of time. Typically, the usable threshold ranges are between
±100 mg and ±500 mg.
8.5.2
Motion detection
Motion detection is often used to alert the main processor that the device is currently in use. When the acceleration exceeds a
set threshold for a set amount of time, the motion interrupt is asserted. A motion can be a fast moving shake or a slow moving
tilt. This will depend on the threshold and timing values configured for the event. The motion detection function can analyze static
acceleration changes or faster jolts. The timing value is set by a configurable debounce counter. The debounce counter acts like
a filter to indicate whether the condition exists for longer than a set amount of time (that is, 100 ms or longer). There is also
directional data available in the source register to detect the direction of the motion that generated the interrupt. This is useful for
applications such as directional shake or flick detection, and can also assist gesture detection algorithms by indicating that a
motion gesture has started.
8.6
Transient detection
FXLS8471Q integrates an acceleration transient detection function that incorporates a high-pass filter. Acceleration data goes
through the high-pass filter, eliminating the DC tilt offset and low frequency acceleration changes. The high-pass filter cutoff can
be set by the user to four different frequencies which are dependent on the selected Output Data Rate (ODR). A higher cutoff
frequency ensures that DC and slowly changing acceleration data will be filtered out, allowing only the higher frequencies to pass.
The transient detection feature can be used in the same manner as the motion detection by bypassing the high-pass filter. There
is an option in the configuration register to do this. This adds more flexibility to cover the various customer use cases.
Many applications use the accelerometer’s static acceleration readings (that is, tilt) which measure the change in acceleration
due to gravity only. These functions benefit from acceleration data being filtered with a low-pass filter where high-frequency data
is considered noise. However, there are many functions where the accelerometer must analyze dynamic acceleration. Functions
such as tap, flick, shake and step counting are based on the analysis of the change in the dynamic acceleration. The transient
detection function can be routed to either interrupt pin through bit 5 in CTRL_REG5 register (0x2E). Registers 0x1D – 0x20 are
used for configuring the transient detection function. The source register contains directional data to determine the direction of
the transient acceleration, either positive or negative. For further information of the embedded transient detection function along
with specific application examples and recommended configuration settings, refer to Freescale application note AN4461.
8.7
Pulse detection
FXLS8471Q has embedded single/double and directional pulse detection. This function employs several timers for programming
the pulse width time and the latency between pulses. The detection thresholds are independently programmable for each axis.
The acceleration data input to the pulse detection circuit can be put through both high and low-pass filters, allowing for greater
flexibility in discriminating between pulse and tap events. The PULSE_SRC register provides information on the axis, direction
(polarity), and single/double event status for the detected pulse or tap. For more information on how to configure the device for
pulse detection, please refer to Freescale application note AN4072.
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8.8
Orientation detection
FXLS8471Q has an embedded orientation detection algorithm with the ability to detect all six orientations. The transition angles
and hysteresis are programmable, allowing for a smooth transition between portrait and landscape orientations.
The angle at which the device no longer detects the orientation change is referred to as the “Z-lockout angle”. The device operates
down to 29° from the flat position. All angles are accurate to ±2°.
For further information on the orientation detection function refer to Freescale application note, AN4068.
8.9
Acceleration Vector-Magnitude detection
FXLS8471Q incorporates an acceleration vector-magnitude change detection block that can be configured to generate an
interrupt when the acceleration magnitude exceeds a preset threshold for a programmed debounce time. The function can be
configured to operate in absolute or relative modes, and can also act as a wake to sleep/sleep to wake source. This function is
useful for detecting acceleration transients when operated in absolute mode, or for detecting changes in orientation when
operated in relative mode, refer to Freescale application note AN4692.
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9
Register Map
Table 13. Register Address Map
Auto-Increment Address
STATUS[f_mode] = 00, STATUS[f_mode] > 00, STATUS[f_mode] = 00, STATUS[f_mode] > 00,
CTRL_REG1[f_read] = 0 CTRL_REG1[f_read] = 0 CTRL_REG1[f_read] = 1 CTRL_REG1[f_read] = 1
Default
Hex
Value
Comment
0x01
0x00
Real-time, data-ready
status or FIFO status
(DR_STATUS or
F_STATUS)
Name
Type
Register
Address
STATUS(1)(2)
R
0x00
OUT_X_MSB(1)(2)
R
0x01
OUT_X_LSB(1)(2)
R
0x02
0x03
OUT_Y_MSB(1)(2)
R
0x03
0x04
OUT_Y_LSB(1)(2)
R
0x04
0x05
OUT_Z_MSB(1)(2)
R
0x05
OUT_Z_LSB(1)(2)
R
0x06
Reserved
—
0x070x08
F_SETUP(1)(3)
R/W
TRIG_CFG
0x02
0x01
0x03
0x01
Data
[7:0] are 8
MSBs of
14-bit
sample.
Root
pointer to
XYZ FIFO
data.
Data
[7:2] are 6 LSBs of
14-bit sample
Data
[7:0] are 8 MSBs of
14-bit sample
0x00
Data
[7:2] are 6 LSBs of
14-bit sample
0x06
0x00
Data
[7:0] are 8 MSBs of
14-bit sample
0x00
0x00
Data
[7:2] are 6 LSBs of
14-bit sample
—
—
Reserved, do not modify
0x09
0x0A
0x00
FIFO setup
R/W
0x0A
0x0B
0x00
FIFO event trigger
configuration register
SYSMOD(1)(2)
R
0x0B
0x0C
Output
Current system mode
INT_SOURCE(1)(2)
R
0x0C
0x0D
Output
Interrupt status
WHO_AM_I(1)
R
0x0D
0x0E
0x6A
Device ID
XYZ_DATA_CFG(1)(4)
R/W
0x0E
0x0F
0x00
Acceleration dynamic
range and filter enable
settings
0x00
0x05
0x00
HP_FILTER_CUTOFF(1)(4)
R/W
0x0F
0x10
0x00
Pulse detection highpass and low-pass filter
enable bits. High-pass
filter cutoff frequency
selection
PL_STATUS(1)(2)
R
0x10
0x11
0x00
Landscape/Portrait
orientation status
PL_CFG(1)(4)
R/W
0x11
0x12
0x83
Landscape/Portrait
configuration.
PL_COUNT(1)(3)
R/W
0x12
0x13
0x00
Landscape/Portrait
debounce counter
PL_BF_ZCOMP(1)(4)
R/W
0x13
0x14
0x00
Back/Front Trip angle
threshold
PL_THS_REG(1)(4)
R/W
0x14
0x15
0x1A
Portrait to Landscape
Trip Threshold angle
and hysteresis settings
A_FFMT_CFG(1)(4)
R/W
0x15
0x16
0x00
Freefall/Motion function
configuration
A_FFMT_SRC(1)(2)
R
0x16
0x17
0x00
Freefall/Motion event
source register
A_FFMT_THS(1)(3)
R/W
0x17
0x18
0x00
Freefall/Motion
threshold register
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Table 13. Register Address Map (Continued)
A_FFMT_COUNT(1)(3)
R/W
0x18
0x19
0x00
Freefall/Motion
debounce counter
Reserved
—
0x190x1C
—
—
Reserved, do not modify
TRANSIENT_CFG(1)(4)
R/W
0x1D
0x1E
0x00
Transient function
configuration
TRANSIENT_SRC(1)(2)
R
0x1E
0x1F
0x00
Transient event status
register
TRANSIENT_THS(1)(3)
R/W
0x1F
0x20
0x00
Transient event
threshold
TRANSIENT_COUNT(1)(3)
R/W
0x20
0x21
0x00
Transient debounce
counter
PULSE_CFG(1)(4)
R/W
0x21
0x22
0x00
Pulse function
configuration
PULSE_SRC(1)(2)
R
0x22
0x23
0x00
Pulse function source
register
PULSE_THSX(1)(3)
R/W
0x23
0x24
0x00
X-axis pulse threshold
PULSE_THSY(1)(3)
R/W
0x24
0x25
0x00
Y-axis pulse threshold
PULSE_THSZ(1)(3)
R/W
0x25
0x26
0x00
Z-axis pulse threshold
PULSE_TMLT(1)(4)
R/W
0x26
0x27
0x00
Time limit for pulse
detection
PULSE_LTCY(1)(4)
R/W
0x27
0x28
0x00
Latency time for
second pulse detection
PULSE_WIND(1)(4)
R/W
0x28
0x29
0x00
Window time for
second pulse detection
ASLP_COUNT(1)(4)
R/W
0x29
0x2A
0x00
In activity counter
setting for Auto-Sleep
CTRL_REG1(1)(4)
R/W
0x2A
0x2B
0x00
System ODR,
accelerometer OSR,
operating mode
CTRL_REG2(1)(4)
R/W
0x2B
0x2C
0x00
Self-Test, Reset,
accelerometer OSR and
Sleep mode settings
CTRL_REG3(1)(4)
R/W
0x2C
0x2D
0x00
Sleep mode interrupt
wake enable, interrupt
polarity, push-pull/opendrain configuration
CTRL_REG4(1)(4)
R/W
0x2D
0x2E
0x00
Interrupt enable register
CTRL_REG5(1)(4)
R/W
0x2E
0x2F
0x00
Interrupt pin (INT1/INT2)
map
OFF_X(1)(4)
R/W
0x2F
0x30
0x00
X-axis accelerometer
offset adjust
OFF_Y(1)(4)
R/W
0x30
0x31
0x00
Y-axis accelerometer
offset adjust
OFF_Z(1)(4)
R/W
0x31
0x32
0x00
Z-axis accelerometer
offset adjust
Reserved
R/W
0x320x5E
—
—
Reserved, do not modify
A_VECM_CFG
R/W
0x5F
0x60
0x00
Acceleration vectormagnitude configuration
register
A_VECM_THS_MSB
R/W
0x60
0x61
0x00
Acceleration vectormagnitude threshold
MSB
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Table 13. Register Address Map (Continued)
A_VECM_THS_LSB
R/W
0x61
0x62
0x00
Acceleration vectormagnitude threshold
LSB
A_VECM_CNT
R/W
0x62
0x63
0x00
Acceleration vectormagnitude debounce
count
A_VECM_INITX_MSB
R/W
0x63
0x64
0x00
Acceleration vectormagnitude X-axis
reference value MSB
A_VECM_INITX_LSB
R/W
0x64
0x65
0x00
Acceleration vectormagnitude X-axis
reference value LSB
A_VECM_INITY_MSB
R/W
0x65
0x66
0x00
Acceleration vectormagnitude Y-axis
reference value MSB
A_VECM_INITY_LSB
R/W
0x66
0x67
0x00
Acceleration vectormagnitude Y-axis
reference value LSB
A_VECM_INITZ_MSB
R/W
0x67
0x68
0x00
Acceleration vectormagnitude Z-axis
reference value MSB
A_VECM_INITZ_LSB
R/W
0x68
0x69
0x00
Acceleration vectormagnitude Z-axis
reference value LSB
Reserved
—
0x690x72
—
—
Reserved, do not modify
A_FFMT_THS_X_MSB
R/W
0x73
0x74
0x00
X-axis FMT threshold
MSB
A_FFMT_THS_X_LSB
R/W
0x74
0x75
0x00
X-axis FFMT threshold
LSB
A_FFMT_THS_Y_MSB
R/W
0x75
0x76
0x00
Y-axis FFMT threshold
MSB
A_FFMT_THS_Y_LSB
R/W
0x76
0x77
0x00
Y-axis FFMT threshold
LSB
A_FFMT_THS_Z_MSB
R/W
0x77
0x78
0x00
Z-axis FFMT threshold
MSB
A_FFMT_THS_Z_LSB
R/W
0x78
0x79
0x00
Z-axis FFMT threshold
LSB
Reserved
—
0x79 0xFF
—
—
Reserved, do not modify
1. Register contents are preserved when transitioning from Active to Standby mode.
2. Register contents are reset when transitioning from Standby to Active mode.
3. Register contents can be modified anytime in Standby or Active mode. A write to this register will cause a reset of the corresponding internal
system debounce counter.
4. Modification of this register’s contents can only occur when device is in Standby mode, except the FS[1:0] bit fields in CTRL_REG1 register.
NOTE
The auto-increment addressing is only enabled when registers are read using burst-read mode when the device is configured for
I2C or SPI. The auto-increment address is automatically reset to 0x00 in I2C mode when a stop condition is detected. In SPI mode
there is no stop condition and the auto-increment address is not automatically reset to 0x00.
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10
Registers by Functional Blocks
10.1
Device configuration
10.1.1
STATUS (0x00) register
Table 14. STATUS register
DR_STATUS or F_STATUS
0
0
0
0
0
0
0
0
Table 15. STATUS Description
Field
Description
F_SETUP[f_mode] = 2’b00
register 0x00 → DR_STATUS
F_SETUP[f_mode] > 2’b00
register 0x00 → F_STATUS
The STATUS register aliases allow for the contiguous burst read of both status and current acceleration sample/FIFO data using
the auto-increment addressing mechanism in both 8- and 14-bit modes.
10.1.2
DR_STATUS (0x00) register
Data-Ready Status when F_SETUP[f_mode] = 0x00
This STATUS register provides the acquisition status information on a per-sample basis, and reflects real-time updates to the
OUT_X, OUT_Y, and OUT_Z registers.
When the FIFO subsystem data output register driver is disabled (F_SETUP[f_mode] = 2’b00), this register indicates the realtime status information of the accelerometer X, Y, and Z axes sample data.
Table 16. DR_STATUS register
zyxow
zow
yow
xow
zyxdr
zdr
ydr
xdr
0
0
0
0
0
0
0
0
Table 17. DR_STATUS description
Field
Description
zyxow
zyxow is set to 1 whenever new data is acquired before completing the retrieval of the previous set. This event occurs when
the content of at least one acceleration data register (that is, OUT_X, OUT_Y, and OUT_Z) has been overwritten. zyxow is
cleared when the high-bytes of the acceleration data (OUT_X_MSB, OUT_Y_MSB, and OUT_Z_MSB) are read.
X, Y, Z-axis data overwrite.
0: No data overwrite has occurred
1: Previous X, Y, Z data was overwritten by new X, Y, Z data before it was completely read
zow
zow is set to 1 whenever a new Z-axis acquisition is completed before the retrieval of the previous data. When this occurs the
previous data is overwritten. zow is cleared anytime OUT_Z_MSB register is read.
Z-axis data overwrite.
0: No data overwrite has occurred
1: Previous Z-axis data was overwritten by new Z-axis data before it was read
yow
yow is set to 1 whenever a new Y-axis acquisition is completed before the retrieval of the previous data. When this occurs the
previous data is overwritten. yow is cleared anytime OUT_Y_MSB register is read.
Y-axis data overwrite.
0: No data overwrite has occurred
1: Previous Y-axis data was overwritten by new Y-axis data before it was read
xow
xow is set to 1 whenever a new X-axis acquisition is completed before the retrieval of the previous data. When this occurs the
previous data is overwritten. xow is cleared anytime OUT_X_MSB register is read.
X-axis data overwrite.
0: No data overwrite has occurred
1: Previous X-axis data was overwritten by new X-axis data before it was read
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Table 17. DR_STATUS description (Continued)
zyxdr
zyxdr signals that a new acquisition for any of the enabled channels is available. zyxdr is cleared when the high-bytes of the
acceleration data (OUT_X_MSB, OUT_Y_MSB, OUT_Z_MSB) are read.
X, Y, Z-axis new data ready.
0: No new set of data ready
1: New set of data is ready
zdr
zdr is set to 1 whenever a new Z-axis data acquisition is completed. zdr is cleared anytime the OUT_Z_MSB register is read.
Z-axis new data available.
0: No new Z-axis data is ready
1: New Z-axis data is ready
ydr
ydr is set to 1 whenever a new Y-axis data acquisition is completed. ydr is cleared anytime the OUT_Y_MSB register is read.
Y-axis new data available. Default value: 0
0: No new Y-axis data ready
1: New Y-axis data is ready
xdr
xdr is set to 1 whenever a new X-axis data acquisition is completed. xdr is cleared anytime the OUT_X_MSB register is read.
X-axis new data available. Default value: 0
0: No new X-axis data ready
1: New X-axis data is ready
10.1.3
F_STATUS (0x00) register
FIFO Status when F_SETUP[f_mode] = 0x00 > 0x00.
If the FIFO subsystem data output register driver is enabled, the status register indicates the current status information of the
FIFO subsystem.
Table 18. F_STATUS register
f_ovf
f_wmrk_flag
f_cnt[5:0]
0
0
0
Table 19. FIFO flag event descriptions
f_ovf
f_wmrk_flag
Event description
0
X
No FIFO overflow events detected.
1
X
FIFO overflow event detected.
X
0
No FIFO watermark event detected.
X
1
A FIFO Watermark event was detected indicating that a FIFO sample count greater than watermark
value has been reached.
If F_SETUP[f_mode] = 2’b11, a FIFO trigger event was detected
The f_ovf and f_wmrk_flag flags remain asserted while the event source is still active, but the user can clear the FIFO interrupt
bit in the interrupt source register (INT_SOURCE) by reading the F_STATUS register. In this case, the INT_SOURCE[src_fifo]
bit will be set again when the next data sample enters the FIFO.
Therefore the f_ovf bit will remain asserted while the FIFO has overflowed and the f_wmrk_flag bit will remain asserted while the
f_cnt value is equal to or greater than then f_wmrk value.
Table 20. FIFO sample count bit description
Field
f_cnt[5:0]
Description
These bits indicate the number of acceleration samples currently stored in the FIFO buffer. Count 6’b000000 indicates
that the FIFO is empty.
FIFO sample counter. Default value 6’b000000.
(6’b000001 to 6’b100000 indicates 1 to 32 samples stored in FIFO
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10.1.4
TRIG_CFG (0x0A) register
FIFO trigger configuration register. After the interrupt flag of the enabled event in TRIG_CFG is set, the FIFO (when configured
in Trigger mode) is gated at the time of the interrupt event preventing the further collection of data samples. This allows the host
processor to analyze the data leading up to the event detection (up to 32 samples). For detailed information on how to utilize the
FIFO and the various trigger events, please see AN4073 available on the Freescale website.
Table 21. TRIG_CFG register
—
—
trig_trans
trig_lndprt
trig_pulse
trig_ffmt
trig_a_vecm
—
0
0
0
0
0
0
0
0
Table 22. TRIG_CFG bit descriptions
Field
Description
trig_trans
Transient interrupt FIFO trigger enable.
trig_lndprt
Landscape/Portrait orientation interrupt FIFO trigger enable.
trig_pulse
Pulse interrupt FIFO trigger enable
trig_ffmt
trig_a_vecm
10.1.5
Freefall/motion interrupt FIFO trigger enable
Acceleration vector-magnitude FIFO trigger enable.
SYSMOD (0x0B) register
Table 23. SYSMOD register
fgerr
fgt[4:0]
sysmod[1:0]
Table 24. SYSMOD bit description
Field
fgerr
fgt[4:0]
sysmod[1:0]
Description
FIFO gate error. Default value: 0.
0: No FIFO gate error detected.
1: FIFO gate error was detected.
Emptying the FIFO buffer clears the fgerr bit in the SYSMOD register.
See CTRL_REG3 [Interrupt CTRL register] (0x2C) for more information on configuring the FIFO Gate function.
Number of ODR time units since fgerr was asserted. Reset when fgerr is cleared
System mode. Default value: 0.
00: Standby mode
01: Wake mode
10: Sleep mode
The system mode register indicates the current device operating mode. Applications using the Auto-Sleep/Auto-Wake
mechanism should use this register to synchronize their application with the device operating mode. The system mode register
also indicates the status of the FIFO gate error flag and the time elapsed since the FIFO gate error flag was asserted.
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10.1.6
INT_SOURCE (0x0C) register
Interrupt source register. The bits that are set (logic ‘1’) indicate which function has asserted its interrupt and conversely bits that
are cleared (logic ‘0’) indicate which function has not asserted its interrupt.
Reading the INT_SOURCE register does not clear any interrupt status bits (except for src_a_vecm, see below); the respective
interrupt flag bits are reset by reading the appropriate source register for the function that generated the interrupt.
Table 25. INT_SOURCE register
src_aslp
src_fifo
src_trans
src_lndprt
src_pulse
src_ffmt
src_a_vecm
src_drdy
Table 26. INT_SOURCE bit descriptions
Field
Description
src_aslp
Auto-Sleep/Wake interrupt status bit: logic ‘1’ indicates that an interrupt event that can cause a Wake to Sleep or Sleep to
Wake system mode transition has occurred and logic ‘0’ indicates that no Wake to Sleep or Sleep to Wake system mode
transition interrupt event has occurred.
The “Wake-to-Sleep” transition occurs when a period of inactivity that exceeds the user-specified time limit
(ASLP_COUNT) has been detected, thus causing the system to transition to a user-specified low ODR setting.
A “Sleep-to-Wake” transition occurs when the user-specified interrupt event has awakened the system, thus causing the
system to transition to the user-specified higher ODR setting.
Reading the SYSMOD register will clear the src_aslp bit.
src_fifo
FIFO interrupt status bit: logic ‘1’ indicates that a FIFO interrupt event such as an overflow or watermark (F_STATUS[f_cnt]
= F_STATUS[f_wmrk]) event has occurred and logic ‘0’ indicates that no FIFO interrupt event has occurred.
This bit is cleared by reading the F_STATUS register.
src_trans
Transient interrupt status bit: logic ‘1’ indicates that an acceleration transient value greater than user-specified threshold
has occurred. and logic ‘0’ indicates that no transient event has occurred.
This bit is asserted whenever TRANSIENT_SRC[ea] is asserted and the functional block interrupt has been enabled.
This bit is cleared by reading the TRANSIENT_SRC register.
src_lndprt
Landscape/Portrait orientation interrupt status bit: logic ‘1’ indicates that an interrupt was generated due to a change in the
device orientation status and logic ‘0’ indicates that no change in orientation status was detected.
This bit is asserted whenever PL_STATUS[newlp] is asserted and the functional block interrupt has been enabled.
This bit is cleared by reading the PL_STATUS register.
src_pulse
Pulse interrupt status bit: logic ‘1’ indicates that an interrupt was generated due to single- and/or double- pulse event and
logic ‘0’ indicates that no pulse event was detected.
This bit is asserted whenever PULSE_SRC[ea] is asserted and the functional block interrupt has been enabled.
This bit is cleared by reading the PULSE_SRC register.
src_ffmt
Freefall/motion interrupt status bit: logic ‘1’ indicates that the freefall/motion function interrupt is active and logic ‘0’
indicates that no freefall or motion event was detected.
This bit is asserted whenever PULSE_SRC[ea] is asserted and the functional block interrupt has been enabled.
This bit is cleared by reading the A_FFMT_SRC register.
src_a_vecm
Accelerometer vector-magnitude interrupt status bit: logic ‘1’ indicates that an interrupt was generated due to acceleration
vector-magnitude function and logic ‘0’ indicates that no interrupt has been generated. This bit is cleared by reading this
register (INT_SOURCE).
src_drdy
Data-ready interrupt status bit. In acceleration only mode this bit indicates that new accelerometer data is available to read.
The src_drdy interrupt flag is cleared by reading out the acceleration data from the OUT_X, OUT_Y, and OUT_Z registers.
This data can be burst read using a 6-byte burst read starting from the address 0x01 (OUT_X_MSB).
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10.1.7
WHO_AM_I (0x0D) register
Table 27. WHO_AM_I register
who_am_i[7:0]
0x6A
Device identification register. This register contains the device identifier which is set to 0x6A.
10.1.8
CTRL_REG1 (0x2A) register
NOTE
Except for Standby mode selection, the device must be in Standby mode to change any of
the fields within CTRL_REG1 (0x2A).
Table 28. CTRL_REG1 register
aslp_rate[1:0]
dr[2:0]
lnoise
f_read
active
0
3’b001
0
0
0
Table 29. CTRL_REG1 bit descriptions
Field
aslp_rate[1:0]
Description
Configures the auto-wake sample frequency when the device is in Sleep mode.
See Table 30 for more information.
dr[2:0]
Output Data Rate (ODR) selection.
See Table 31 for more information.
lnoise
Reduced noise and full-scale range mode (analog gain times 2).
0: Normal mode
1: Reduced noise mode; Note that the FSR setting is restricted to a ±4 g in this mode (lnoise = 1).
f_read
Fast-read mode: Data format is limited to the 8-bit MSB for accelerometer output data. The auto-address pointer will skip over
the LSB addresses for each axes sample data when performing a burst read operation.
0: Normal mode
1: Fast-read mode
active
Standby/Active.
0: Standby mode
1: Active mode
Table 30. Sleep mode poll rate description
aslp_rate1
aslp_rate0
Frequency (Hz)
0
0
50
0
1
12.5
1
0
6.25
1
1
1.56
It is important to note that when the device is in Auto-Sleep mode, the system ODR and data rate for all the system functional
blocks is overridden by the sleep data rate set by the aslp_rate field..
Table 31 shows the various system output data rates (ODR) that may be selected using the dr[2:0] bits.
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Table 31. System Output Data Rate selection
dr2
dr1
dr0
ODR (Hz)
Period (ms)
0
0
0
800.0
1.25
0
0
1
400.0
2.5
0
1
0
200.0
5
0
1
1
100.0
10
1
0
0
50.0
20
1
0
1
12.5
80
1
1
0
6.25
160
1
1
1
1.5625
640
The active bit selects between Standby mode and Active mode. The default value is 0 (Standby mode) on reset.
The lnoise bit selects between normal full dynamic range mode and a high sensitivity, low-noise mode. In low-noise mode the
maximum signal that can be measured is ±4 g. Note: Any thresholds set above 4 g will not be reached.
The f_read bit selects between normal and fast-read modes where the auto-increment counter will also skip over the LSB data
bytes when f_read = 1. All of the acceleration data MSB’s can be read out with a single 3-byte burst read starting at the
OUT_X_MSB register when f_read = 1.
NOTE
The f_read bit can only be changed while F_SETUP[f_mode] = 0.
10.1.9
CTRL_REG2 (0x2B) register
Table 32. CTRL_REG2 register
st
rst
—
smods[1:0]
slpe
mods[1:0]
0
0
0
0
0
0
Table 33. CTRL_REG2 bit descriptions
Field
Description
The st bit activates the accelerometer self-test function. When st is set to 1, a change will occur in the device output levels for
each axis, allowing the host application to check the functionality of the transducer and measurement signal chain.
Self-Test Enable:
st
0: Self-Test disabled
1: Self-Test enabled.
The rst bit is used to initiate a software reset. The reset mechanism can be enabled in both Standby and Active modes. When the
rst bit is set, the boot mechanism resets all functional block registers and loads the respective internal registers with their default
values. Note that the current revision of FXLS8471Q silicon, as identified by a WHO_AM_I value of 0x6A, has an errata
associated with the software reset mechanism when the device is operated in SPI mode. Refer to Appendix A.1 for further
information and a suggested work-around. After setting the rst bit, the system will automatically transition to Standby mode.
Therefore, if the system was already in Standby mode, the reboot process will immediately begin; else if the system was in Active
mode the boot mechanism will automatically transition the system from Active mode to Standby mode, only then can the reboot
process begin. A system reset can also be initiated by pulsing the external RST pin high.
rst
The I2C and SPI communication systems are also reset to avoid corrupted data transactions. The host application should allow
1 ms between issuing a software (setting rst bit) or hardware (pulsing RST pin) reset and attempting communications with the
device over the I2C or SPI interfaces. When the SPI interface mode is desired and multiple devices are present on the bus, make
sure that the bus is quiet (all slave device MISO pins are high-z) during this 1 ms period to ensure the device does not
inadvertently enter I2C mode. See Section 6.2.3 for further information about the interface mode auto-detection circuit.
At the end of the boot process, the rst bit is hardware cleared.
0: Device reset disabled
1: Device reset enabled.
smods[1:0] Sleep mode power scheme selection. See Table 34 for more information.
Auto-Sleep mode enable:
slpe(1)
0: Auto-Sleep is not enabled
1: Auto-Sleep is enabled.
Accelerometer OSR selection. This setting, along with the ODR selection determines the Active mode power and RMS noise for
mods[1:0]
acceleration measurements. See Table 34 for more information.
1. When SLPE = 1, a transition between Sleep mode and Wake mode results in a FIFO flush and a reset of internal functional block counters.
All functional block status information is preserved except where otherwise indicated. For further information, refer to the CTRL_REG3 register
description (fifo_gate bit).
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Table 34. CTRL_REG2[mods] oversampling modes
(s)mods1
(s)mods0
Power mode
0
0
Normal
0
1
Low Noise, Low Power
1
0
High Resolution
1
1
Low Power
Table 35. Oversampling Ratio versus oversampling mode
Accelerometer OSR
ODR (Hz)
Normal
Low Noise, Low Power
High Resolution
Low Power
1.5625
128
32
1024
16
6.25
32
8
256
4
12.5
16
4
128
2
50
4
4
32
2
100
4
4
16
2
200
4
4
8
2
400
4
4
4
2
800
2
2
2
2
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10.1.10 CTRL_REG3 [Interrupt Control Register] (0x2C) register
Table 36. CTRL_REG3 register
fifo_gate
wake_trans
wake_lndprt
wake_pulse
wake_ffmt
wake_en_a_vecm
ipol
pp_od
0
0
0
0
0
0
0
0
Table 37. CTRL_REG3 bit descriptions
Field
Description
fifo_gate
0: FIFO gate is bypassed. FIFO is flushed upon the system mode transitioning from Wake-to-Sleep mode or from Sleepto-Wake mode.
1: The FIFO input buffer is blocked when transitioning from “Wake-to-Sleep” mode or from “Sleep-to-Wake” mode until
the FIFO is flushed.(1) Although the system transitions from “Wake-to-Sleep” or from “Sleep-to-Wake” the contents of the
FIFO buffer are preserved, new data samples are ignored until the FIFO is emptied by the host application.
If the fifo_gate bit is set to logic ‘1’ and the FIFO buffer is not emptied before the arrival of the next sample, then the
SYSMOD[fgerr] will be asserted. The SYSMOD[fgerr] bit remains asserted as long as the FIFO buffer remains unemptied.
Emptying the FIFO buffer clears the SYS_MOD[fgerr] register.
wake_tran
0: Transient function is disabled in Sleep mode
1: Transient function is enabled in Sleep mode and can generate an interrupt to wake the system
wake_lndprt
0: Orientation function is disabled Sleep mode.
1: Orientation function is enabled in Sleep mode and can generate an interrupt to wake the system
wake_pulse
0: Pulse function is disabled in Sleep mode
1: Pulse function is enabled in Sleep mode and can generate an interrupt to wake the system
wake_ffmt
wake_en_a_vecm
ipol
pp_od
0: Freefall/motion function is disabled in Sleep mode
1: Freefall/motion function is enabled in Sleep mode and can generate an interrupt to wake the system
0: Acceleration vector-magnitude function is disabled in Sleep mode
1: Acceleration vector-magnitude function is enabled in Sleep mode and can generate an interrupt to wake the system
The ipol The bit selects the logic polarity of the interrupt signals output on the INT1 and INT2 pins.
INT1/INT2 interrupt logic polarity:
0: Active low (default)
1: Active high
INT1/INT2 push-pull or open-drain output mode selection. The open-drain configuration can be used for connecting
multiple interrupt signals on the same interrupt line but will require an external pullup resistor to function correctly.
0: Push-pull (default)
1: Open-drain
1. The FIFO contents are flushed whenever the system ODR changes in order to prevent the mixing of FIFO data from different ODR periods.
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10.1.11 CTRL_REG4 [Interrupt Enable Register] (0x2D) register
Table 38. CTRL_REG4 register
int_en_aslp
int_en_fifo
int_en_trans
int_en_lndprt
int_en_pulse
int_en_ffmt
int_en_a_vecm
int_en_drdy
0
0
0
0
0
0
0
0
Table 39. Interrupt Enable Register bit descriptions
Field
Description
int_en_aslp
Sleep interrupt enable
0: Auto-Sleep/Wake interrupt disabled
1: Auto-Sleep/Wake interrupt enabled
int_en_fifo
FIFO interrupt enable
0: FIFO interrupt disabled
1: FIFO interrupt enabled
int_en_trans
Transient interrupt enable
0: Transient interrupt disabled
1: Transient interrupt enabled
int_en_lndprt
Orientation interrupt enable
0: Orientation (Landscape/Portrait) interrupt disabled
1: Orientation (Landscape/Portrait) interrupt enabled
int_en_pulse
Pulse interrupt enable
0: Pulse detection interrupt disabled
1: Pulse detection interrupt enabled
int_en_ffmt
Freefall/motion interrupt enable
0: Freefall/motion interrupt disabled
1: Freefall/motion interrupt enabled
int_en_a_vecm
int_en_drdy
Acceleration vector-magnitude interrupt enable
0: Acceleration vector-magnitude interrupt disabled
1: Acceleration vector-magnitude interrupt enabled
Data-ready interrupt enable
0: Data-ready interrupt disabled
1: Data-ready interrupt enabled
The corresponding functional block interrupt enable bit allows the functional block to route its event detection flag to the system’s
interrupt controller. The interrupt controller routes the enabled interrupt signals to either the INT1 or INT2 pins depending on the
settings made in CTRL_REG5.
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10.1.12 CTRL_REG5 [Interrupt Routing Configuration Register] (0x2E) register
Table 40. CTRL_REG5 register
int_cfg_aslp
int_cfg_fifo
int_cfg_trans
int_cfg_lndprt
int_cfg_pulse
int_cfg_ffmt
int_cfg_a_vecm
int_cfg_drdy
0
0
0
0
0
0
0
0
Table 41. Interrupt Routing Configuration bit descriptions
Field
Description
int_cfg_aslp
Sleep interrupt routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
int_cfg_fifo
FIFO interrupt routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
int_cfg_trans
Transient detection interrupt routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
int_cfg_lndprt
Orientation detection interrupt routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
int_cfg_pulse
Pulse detection interrupt routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
int_cfg_ffmt
int_cfg_a_vecm
int_cfg_drdy
Freefall/motion detection interrupt routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin
Acceleration vector-magnitude interrupt routing
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin.
INT1/INT2 configuration.
0: Interrupt is routed to INT2 pin
1: Interrupt is routed to INT1 pin.
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Data Ready
Freefall/Motion Detection
Pulse Detection
INT1
Orientation Detection
INTERRUPT
CONTROLLER
Transient Acceleration Detection
INT2
Auto-Sleep
Acceleration Vector-magnitude
FIFO Interrupt
9
9
INT ENABLE
INT CFG
Figure 10. Interrupt controller block diagram
The system’s interrupt controller uses the corresponding bit field in the CTRL_REG5 register to determine the routing for the INT1
and INT2 interrupt pins. For example, if the int_cfg_drdy bit value is logic ‘0’ the functional block’s interrupt is routed to INT2, and
if the bit value is logic ‘1’ then the interrupt is routed to INT1. All interrupt signals routed to either INT1 or INT2 are logically OR’ed
together as illustrated in Figure 11, thus one or more functional blocks can assert an interrupt pin simultaneously; therefore a
host application responding to an interrupt should read the INT_SOURCE register to determine the source(s) of the interrupt(s).
SRC_RTS
SRC_DRDY
INT1
SRC_FF_MT
OR
SRC_PULSE
OR
INT2
SRC_FIFO
Figure 11. INT1/INT2 PIN Control Logic
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10.2
Auto-Sleep trigger
10.2.1
ASLP_COUNT (0x29) register
The ASLP_COUNT register sets the minimum time period of event flag inactivity required to initiate a change from the current
active mode ODR value specified in CTRL_REG1[dr] to the Sleep mode ODR value specified in CTRL_REG1[aslp_rate],
provided that CTRL_REG2[slpe] = 1.
See Table 45 for functional blocks that may be monitored for inactivity in order to trigger the return-to-sleep event.
Table 42. ASLP_COUNT register
aslp_cnt[7:0]
8’b00000000
Table 43. ASLP_COUNT bit description
Field
Description
aslp_cnt[7:0]
See Table 44 for details
Table 44. ASLP_COUNT relationship with ODR
Output Data Rate (ODR)
Maximum inactivity time (s)
ODR time step (ms)
ASLP_COUNT step (ms)
800
81
1.25
320
400
81
2.5
320
200
81
5
320
100
81
10
320
50
81
20
320
12.5
81
80
320
6.25
81
160
320
1.56
63
640
640
Table 45. Sleep/Wake mode gates and triggers
*
Interrupt source
Event restarts time and
delays Return-to-Sleep
Event will Wake-from-Sleep
SRC_FIFO
Yes
No
SRC_TRANS
Yes
Yes
SRC_LNDPRT
Yes
Yes
SRC_PULSE
Yes
Yes
SRC_FFMT
Yes
Yes
SRC_ASLP
No*
No*
SRC_AVECM
Yes
Yes
If the fifo_gate bit is set to logic ‘1’, the assertion of the SRC_ASLP interrupt does not prevent the system from transitioning to Sleep or from Wake mode; instead
it prevents the FIFO buffer from accepting new sample data until the host application flushes the FIFO buffer.
The interrupt sources listed in Table 45 affect the auto-sleep, return to sleep and wake from sleep mechanism only if they have
been previously enabled. The functional block event flags that are bypassed while the system is in Auto-Sleep mode are
temporary disabled (see Section 10.1.10, “CTRL_REG3 [Interrupt Control Register] (0x2C) register,” on page 35 for more
information) and are automatically re-enabled when the device returns from Auto-Sleep mode (that is, wakes up), except for the
data ready function.
If any of the interrupt sources listed under the Return-to-Sleep column is asserted before the sleep counter reaches the value
specified in ASLP_COUNT, then all sleep mode transitions are terminated and the internal sleep counter is reset. If none of the
interrupts listed under the Return-to-Sleep column are asserted within the time limit specified by the ASLP_COUNT register, the
system will transition to the Sleep mode and use the ODR value specified in CTRL_REG1[aslp_rate].
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If any of the interrupt sources listed under the “Wake-from-Sleep” column is asserted, then the system will transition out of the
low sample rate Auto-Sleep mode to the user-specified fast sample rate provided the user-specified wake event function is
enabled in register CTRL_REG3.
If the Auto-Sleep interrupt is enabled, a transition from Active mode to Sleep mode and vice-versa will generate an interrupt.
If CTRL_REG3[fifo_gate] = 1, transitioning to Auto-Sleep mode will preserve the FIFO contents, set SYSMOD[fgerr] (FIFO Gate
error), and stop new acquisitions. The system will wait for the FIFO buffer to be emptied by the host application before new
samples can be acquired.
Acquire
Standby
No Sleep
SLP_COUNTER <
ASLP COUNT
SLP_COUNTER >
ASLP COUNT
Active Mode
Standby
Sleep
Auto-Sleep Mode
Figure 12. Auto-Sleep state transition diagram
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10.3
Output data registers
10.3.1
OUT_X_MSB (0x01), OUT_X_LSB (0x02), OUT_Y_MSB (0x03), OUT_Y_LSB (0x04),
OUT_Z_MSB (0x05), OUT_Z_LSB (0x06) registers
These registers contain the X-axis, Y-axis, and Z-axis 14-bit left-justified sample data expressed as 2's complement numbers.
The sample data output registers store the current sample data if the FIFO buffer function is disabled, but if the FIFO buffer
function is enabled the sample data output registers then point to the head of the FIFO buffer which contains up to the previous
32 X, Y, and Z data samples.
The data is read out in the following order: Xmsb, Xlsb, Ymsb, Ylsb, Zmsb, Zlsb for CTRL_REG1[f_read] = 0, and Xmsb, Ymsb,
Zmsb for CTRL_REG1[f_read] = 1. Similarly, for CTRL_REG1[f_read] = 1, only the MSB's of the acceleration data are read out
in the same axis order.
If the CTRL_REG1[f_read] bit is set, auto-increment will skip over the LSB registers. This will shorten the data acquisition from
6 bytes to 3 bytes. If the LSB registers are directly addressed, the LSB information can still be read regardless of the
CTRL_REG1[f_read] register setting.
If the FIFO data output register driver is enabled (F_SETUP[f_mode] > 00), register 0x01 points to the head of the FIFO buffer,
while registers 0x02, 0x03, 0x04, 0x05, 0x06 return a value of zero when read directly.
The DR_STATUS registers, OUT_X_MSB, OUT_X_LSB, OUT_Y_MSB, OUT_Y_LSB, OUT_Z_MSB, and OUT_Z_LSB are
located in the auto-incrementing address range of 0x00 to 0x06, allowing all of the acceleration data to be read in a single-burst
read of 6 bytes starting at the OUT_X_MSB register.
Table 46. OUT_X_MSB register
xd[13:6]
Table 47. OUT_X_LSB register
xd[5:0]
—
—
—
—
—
—
Table 48. OUT_Y_MSB register
yd[13:6]
Table 49. OUT_Y_LSB register
yd[5:0]
Table 50. OUT_Z_MSB register
zd[13:6]
Table 51. OUT_Z_LSB register
zd[5:0]
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10.4
FIFO
10.4.1
F_SETUP (0x09) register
Table 52. F_SETUP register
f_mode[1:0]
f_wmrk[5:0]
0
6b’000000
Table 53. F_SETUP bit descriptions
Field
Description
f_mode[1:0](1)(2)(3)
FIFO buffer operating mode.
00: FIFO is disabled.
01: FIFO contains the most recent samples when overflowed (circular buffer). Oldest sample is discarded to be replaced
by new sample.
10: FIFO stops accepting new samples when overflowed.
11: FIFO trigger mode.
The FIFO is flushed whenever the FIFO is disabled, during an automatic ODR change (Auto-Wake/Sleep), or on a
transition from Standby mode to Active mode.
Disabling the FIFO (f_mode = 2’b00) resets the F_STATUS[f_ovf], F_STATUS[f_wmrk_flag], F_STATUS[f_cnt] status
flags to zero.
A FIFO overflow event (that is, F_STATUS[f_cnt] = 32) will assert the F_STATUS[f_ovf] flag.
f_wmrk[5:0](2)
FIFO sample count watermark.
These bits set the number of FIFO samples required to trigger a watermark interrupt. A FIFO watermark event flag
F_STATUS[f_wmk_flag] is raised when FIFO sample count F_STATUS[f_cnt] value is equal to or greater than the
f_ wmrk watermark.
Setting the f_wmrk to 6’b000000 will disable the FIFO watermark event flag generation.
This field is also used to set the number of pre-trigger samples in trigger mode (f_mode = 2’b11).
1. This bit field can be written in Active mode.
2. This bit field can be written in Standby mode.
3. The FIFO mode (f_mode) cannot be switched between operational modes (01, 10 and 11).
A FIFO sample count exceeding the watermark event does not stop the FIFO from accepting new data.
The FIFO update rate is dictated by the selected system ODR. In Active mode the ODR is set by CTRL_REG1[dr] and when
Auto-Sleep is active, the ODR is set by CTRL_REG1[aslp_rate] bit fields.
When data is read from the FIFO buffer, the oldest sample data in the buffer is returned and also deleted from the front of the
FIFO, while the FIFO sample count is decremented by one. It is assumed that the host application will use the I2C or SPI burst
read transactions to dump the FIFO contents. If the FIFO X, Y, and Z data is not completely read in one burst read transaction,
the next read will start at the next FIFO location X-axis data. If the Y or Z data is not read out in the same burst transaction as
the X-axis data, it will be lost.
In Trigger mode, the FIFO is operated as a circular buffer and will contain up to the 32 most recent acceleration data samples.
The oldest sample is discarded and replaced by the current sample, until a FIFO trigger event occurs. After a trigger event occurs,
the FIFO will continue to accept samples only until overflowed, after which point the newest sample data is discarded. For more
information on using the FIFO buffer and the various FIFO operating modes, please refer to Freescale application note AN4073.
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10.5
Sensor data configuration
10.5.1
XYZ_DATA_CFG (0x0E) register
The XYZ_DATA_CFG register is used to configure the desired acceleration full-scale range, and also to select whether the output
data is passed through the high-pass filter.
Table 54. XYZ_DATA_CFG register
—
—
—
hpf_out
—
—
fs[1:0]
0
0
0
0
0
0
0
Table 55. XYZ_DATA_CFG bit descriptions
Field
Description
hpf_out
fs[1:0]
Enable high-pass filter on acceleration output data
1: Output data is high-pass filtered
0: High-pass filter is disabled.
Accelerometer full-scale range selection. See Table 56
Table 56.
fs[1]
fs[0]
Full-Scale range
0
0
±0.244 mg/LSB
0
1
±0.488 mg/LSB
1
0
±0.976 mg/LSB
1
1
Reserved
10.6
High-Pass filter
10.6.1
HP_FILTER_CUTOFF (0x0F) register
High-pass filter cutoff frequency setting register.
Table 57. HP_FILTER_CUTOFF register
—
—
pulse_hpf_byp
pulse_lpf_en
—
—
sel[1:0]
0
0
0
0
0
0
0
Table 58. HP_FILTER_CUTOFF bit descriptions
Field
Description
pulse_hpf_byp
Bypass high-pass filter for pulse processing function
0: HPF enabled for pulse processing
1: HPF bypassed for pulse processing
pulse_lpf_en
Enable low-pass filter for pulse processing function
0: LPF disabled for pulse processing
1: LPF enabled for pulse processing
sel[1:0]
HPF cutoff frequency selection
See Table 59.
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Table 59. HP_FILTER_CUTOFF
High-Pass cutoff frequency (Hz)
sel = 2’b00
ODR (Hz)
sel = 2’b01
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
Low power
800
16
16
16
16
8
8
8
8
400
16
16
16
8
8
8
8
4
200
8
8
16
4
4
4
8
2
100
4
4
16
2
2
2
8
1
50
2
2
16
1
1
1
8
0.5
12.5
2
0.5
16
0.25
1
0.25
8
0.125
6.25
2
0.25
16
0.125
1
0.125
8
0.063
1.56
2
0.063
16
0.031
1
0.031
8
0.016
sel = 2’b10
ODR (Hz)
sel = 2’b11
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
Low power
800
4
4
4
4
2
2
2
2
400
4
4
4
2
2
2
2
1
200
2
2
4
1
1
1
2
0.5
100
1
1
4
0.5
0.5
0.5
2
0.25
50
0.5
0.5
4
0.25
0.25
0.25
2
0.125
12.5
0.5
0.125
4
0.063
0.25
0.063
2
0.031
6.25
0.5
0.063
4
0.031
0.25
0.031
2
0.016
1.56
0.5
0.016
4
0.008
0.25
0.008
2
0.004
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10.7
Portrait/Landscape Detection
The FXLS8471Q is capable of detecting six orientations: Landscape Left, Landscape Right, Portrait Up, and Portrait Down with
Z-lockout feature as well as Face Up and Face Down orientation as shown in Figures 13, 14 and 15. For more details on the
meaning of the different user-configurable settings and for example code, please refer to Freescale application note AN4068.
90°
NORMAL
DETECTION
Z-LOCK = 32.142°
LOCKOUT
REGION
0°
Figure 13. Illustration of Z-tilt angle lockout transition
.
Portrait
90°
Landscape to Portrait
Trip Angle = 60°
0° Landscape
Figure 14. Illustration of landscape to portrait transition
.
Portrait
90°
Portrait to Landscape
Trip Angle = 30°
0° Landscape
Figure 15. Illustration of portrait to landscape transition
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10.7.1
PL_STATUS (0x10) register
This status register can be read to get updated information on any change in orientation by reading bit 7, or the specifics of the
orientation by reading the other bits. For further understanding of Portrait Up, Portrait Down, Landscape Left, Landscape Right,
Back and Front orientations please refer to Figure 15. The interrupt is cleared when reading the PL_STATUS register.
Table 60. PL_STATUS register
newlp
lo
—
—
—
lapo[1]
lapo[0]
bafro
0
0
0
0
0
0
0
0
Table 61. PL_STATUS bit descriptions
Field
newlp
lo
lapo[1:0](1)
bafro
Description
Landscape/Portrait status change flag.
0: No change
1: BAFRO and/or LAPO and/or Z-tilt lockout value has changed
Z-tilt angle lockout.
0: Lockout condition has not been detected.
1: Z-tilt lockout trip angle has been exceeded. Lockout condition has been detected.
Landscape/Portrait orientation.
00: Portrait up: equipment standing vertically in the normal orientation
01: Portrait down: equipment standing vertically in the inverted orientation
10: Landscape right: equipment is in landscape mode to the right
11: Landscape left: equipment is in landscape mode to the left.
Back or front orientation.
0: Front: equipment is in the front facing orientation.
1: Back: equipment is in the back facing orientation.
1. The default powerup state is bafro(Undefined), lapo(Undefined), and no lockout for orientation function.
The newlp bit is set to 1 after the first orientation detection after a Standby to Active transition, and whenever a change in lo, bafro,
or lapo occurs. The newlp bit is cleared anytime the PL_STATUS register is read. lapo, bafro and lo continue to change when
newlp is set. The current orientation is locked if the absolute value of the acceleration experienced on any of the three axes is
greater than 1.25 g.
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10.7.2
PL_CFG (0x11) register
This register enables the Portrait/Landscape function and sets the behavior of the debounce counter.
Table 62. PL_CFG register
dbcntm
pl_en
—
—
—
—
—
—
1
0
0
0
0
0
0
0
Table 63. PL_CFG bit descriptions
Field
dbcntm
pl_en
10.7.3
Description
Debounce counter mode selection.
0: Decrements debounce whenever condition of interest is no longer valid.
1: Clears counter whenever condition of interest is no longer valid.
Portrait/Landscape detection enable.
0: Portrait/Landscape detection is disabled.
1: Portrait/Landscape detection is enabled.
PL_COUNT (0x12) register
This register sets the debounce count for the orientation state transition. The minimum debounce latency is determined by the
system ODR value and the value of the PL_COUNT register. Any change to the system ODR or a transition from Active to
Standby (or vice-versa) resets the internal landscape/portrait internal debounce counters.
Table 64. PL_COUNT register
dbnce[7:0]
8’b00000000
Table 65. PL_Count Relationship with the ODR
Max time range (s)
ODR (Hz)
Time step (ms)
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
Low power
800
0.319
0.319
0.319
0.319
1.25
1.25
1.25
1.25
400
0.638
0.638
0.638
0.638
2.5
2.5
2.5
2.5
200
1.28
1.28
0.638
1.28
5
5
2.5
5
100
2.55
2.55
0.638
2.55
10
10
2.5
10
50
5.1
5.1
0.638
5.1
20
20
2.5
20
12.5
5.1
20.4
0.638
20.4
20
80
2.5
80
6.25
5.1
20.4
0.638
40.8
20
80
2.5
160
1.56
5.1
20.4
0.638
40.8
20
80
2.5
160
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10.7.4
PL_BF_ZCOMP (0x13) register
Back/Front and Z-tilt angle compensation register
Table 66. PL_BF_ZCOMP register
bkfr[1:0]
—
—
—
zlock[2:0]
2’b10
0
0
0
3’b100
Table 67. PL_BF_ZCOMP bit descriptions
Field
Description
zlock[2:0]
Z-lock angle threshold. range is from approximately 13° to 44°. Step size is approximately 4°. See Table 68 for more information.
Default value: 0x04 → ∼28°.
Maximum value: 0x07 → ~44°.
bkfr[1:0]
Back/front trip angle threshold. See Table 69 for more information.
Default: 2’b10 → ±70°. Step size is 5°.
Range: ±(65° to 80°).
Table 68. Z-lockout angle definitions
zlock
Resultant angle (min) for positions
between Landscape and Portrait
Resultant angle (max) for
ideal Landscape or Portrait
0x00
13.6°
14.5°
0x01
17.1°
18.2°
0x02
20.7°
22.0°
0x03
24.4°
25.9°
0x04
28.1°
30.0°
0x05
32.0°
34.2°
0x06
36.1°
38.7°
0x07
40.4°
43.4°
Table 69. Back/Front orientation definitions
bkfr
Back → Front Transition
Front → Back Transition
00
Z < 80° or Z > 280°
Z > 100° and Z < 260°
01
Z < 75° or Z > 285°
Z > 105° and Z < 255°
10
Z < 70° or Z > 290°
Z > 110° and Z < 250°
11
Z < 65° or Z > 295°
Z > 115° and Z < 245°
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10.7.5
PL_THS_REG (0x14) register
Portrait to landscape trip threshold registers.
Table 70. PL_THS_REG register
pl_ths[4:0]
hys[2:0]
5’b01000
3’b100
Table 71. Threshold angle lookup table
pl_ths[4:0] value
Threshold angle (approx.)
0x07
15°
0x09
20°
0x0C
30°
0x0D
35°
0x0F
40°
0x10
45°
0x13
55°
0x14
60°
0x17
70°
0x19
75°
Table 72. Trip angles versus hysteresis settings
hys[2:0] value
Landscape to Portrait trip angle
Portrait to Landscape trip angle
0
45°
45°
1
49°
41°
2
52°
38°
3
56°
34°
4
59°
31°
5
62°
28°
6
66°
24°
7
69°
21°
Table 73. Portrait/Landscape ideal orientation definitions
10.8
Position
Description
PU
y ~ -1 g, x ~ 0
PD
y ~ +1 g, x ~ 0
LR
y ~ 0, x ~ +1 g
LL
y ~ 0, x ~ -1 g
Freefall and Motion detection
The Freefall/Motion detection block can be configured to detect low-g (freefall) or high-g (motion) events utilizing the
A_FFMT_CFG[a_ffmt_oae] bit.
In low-g detect mode (A_FFMT_CFG[a_ffmt_oae] = 0) a low-g condition will need to occur on all enabled axes (ex. X, Y and Z)
for the A_FFMT_SRC[a_ffmt_ea] bit to be affected. And, in high-g detect mode (A_FFMT_CFG[a_ffmt_oae] = 1) a high-g
condition occurring in any of the enabled axes (ex. X, Y or Z) will suffice to affect the A_FFMT_SRC[a_ffmt_ea] bit.
The detection threshold(s) are programed in register 0x17 (A_FFMT_THS) for common threshold operation, and 0x73-0x78
(A_FFMT_THS_X/Y/Z) for individual axis threshold operation.
A_FFMT_CFG[a_ffmt_ele] bit determines the behavior of A_FFMT_SRC[a_ffmt_ea] bit in response to the desired acceleration
event (low-g/high-g). When A_FFMT_CFG[a_ffmt_ele] = 1, the freefall or motion event is latched and the
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A_FFMT_SRC[a_ffmt_ea] flag can only be cleared by reading the A_FFMT_SRC register. When A_FFMT_CFG[a_ffmt_ele] = 0,
freefall or motion events are not latched, and the A_FFMT_SRC[a_ffmt_ea] bit reflects the real-time status of the event detection.
A_FFMT_THS[a_ffmt_dbcntm] bit determines the debounce filtering behavior of the logic which sets the
A_FFMT_SRC[a_ffmt_ea] bit. See Figure 17 for details.
It is possible to enable/disable each axis used in the freefall/motion detection function by configuring bits
A_FFMT_CFG[a_ffmt_xefe], A_FFMT_CFG[a_ffmt_yefe], and A_FFMT_CFG[a_ffmt_zefe].
The freefall/motion detection function has the option to use a common 7-bit unsigned threshold for each of the X, Y, Z axes, or
individual unsigned 13-bit thresholds for each axis. When A_FFMT_THS_X_MSB[a_ffmt_ths_xyz_en] = 0, the 7-bit threshold
value stored in register 0x17 is used as a common 7-bit threshold for the X, Y, and Z axes. When a_ffmt_ths_xyz_en = 1, each
axis may be programmed with an individual 13-bit threshold (stored in the A_FFMT_X/Y/Z MSB and LSB registers).
10.8.1
A_FFMT_CFG (0x15) register
Freefall/motion configuration register.
Table 74. A_FFMT_CFG register
a_ffmt_ele
a_ffmt_oae
a_ffmt_zefe
a_ffmt_yefe
a_ffmt_xefe
—
—
—
0
0
0
0
0
0
0
0
Table 75. A_FFMT_CFG bit descriptions
Field
Description
a_ffmt_ele
a_ffmt_ele denotes whether the enabled event flag will be latched in the A_FFMT_SRC register or the event flag status in the
A_FFMT_SRC will indicate the real-time status of the event. If a_ffmt_ele bit is set to a logic ‘1’, then the event flags are frozen
when the a_ffmt_ea bit gets set, and are cleared by reading the A_FFMT_SRC source register.
Default value: 0
0: Event flag latch disabled
1: Event flag latch enabled
a_ffmt_oae
a_ffmt_oae bit allows the selection between motion (logical OR combination of high-g X, Y, Z-axis event flags) and freefall
(logical AND combination of low-g X, Y, Z-axis event flags) detection.
Motion detect/freefall detect logic selection.
Default value: 0 (freefall flag)
0: Freefall flag (Logical AND combination of low-g X, Y, Z-axis event flags)
1: Motion flag (Logical OR combination of high-g X, Y, Z event flags)
a_ffmt_zefe
a_ffmt_zefe enables the detection of a high- or low-g event when the measured acceleration data on Z-axis is above/below
the threshold set in the A_FFMT_THS register. If the a_ffmt_ele bit is set to logic ‘1’ in the A_FFMT_CFG register, new event
flags are blocked from updating the A_FFMT_SRC register.
Default value: 0
0: Event detection disabled
1: Raise event flag on measured Z-axis acceleration above/below threshold.
a_ffmt_yefe
a_ffmt_yefe enables the detection of a high- or low-g event when the measured acceleration data on Y-axis is above/below
the threshold set in the A_FFMT_THS register. If the a_ffmt_ele bit is set to logic ‘1’ in the A_FFMT_CFG register, new event
flags are blocked from updating the A_FFMT_SRC register.
Default value: 0
0: Event detection disabled
1: Raise event flag on measured Y-axis acceleration above/below threshold.
a_ffmt_xefe
a_ffmt_xefe enables the detection of a high- or low-g event when the measured acceleration data on X-axis is above/below
the threshold set in the A_FFMT_THS register. If the a_ffmt_ele bit is set to logic ‘1’ in the A_FFMT_CFG register, new event
flags are blocked from updating the A_FFMT_SRC register.
Default value: 0
0: Event detection disabled
1: Raise event flag on measured X-axis acceleration above/below threshold.
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10.8.2
A_FFMT_SRC (0x16) register
Freefall/motion source register. Read-only register.
This register keeps track of the acceleration event which is triggering (or has triggered, in case of A_FFMT_CFG[a_ffmt_ele]
= 1) the event flag. In particular A_FFMT_SRC[a_ffmt_ea] is set to a logic ‘1’ when the logical combination of acceleration event
flags specified in A_FFMT_CFG register is true. This bit is used in combination with the values in CTRL_REG4[int_en_ffmt] and
CTRL_REG5[int_cfg_ffmt] register bits to generate the freefall/motion interrupts.
Table 76. A_FFMT_SRC register
a_ffmt_ea
—
a_ffmt_zhe
a_ffmt_zhp
a_ffmt_yhe
a_ffmt_yhp
a_ffmt_xhe
a_ffmt_xhp
0
0
0
0
0
0
0
0
Table 77. A_FFMT_SRC bit descriptions
Field
Description
a_ffmt_ea
Event active flag. Default value: 0
0: No event flag has been asserted
1: One or more event flag has been asserted. See the description of the A_FFMT_CFG[a_ffmt_oae] bit to determine the
effect of the 3-axis event flags on the a_ffmt_ea bit.
a_ffmt_zhe
Z-high event flag. Default value: 0
0: Event detected
1: Z-high event has been detected
This bit always reads zero if the a_ffmt_zefe control bit is set to zero
a_ffmt_zhp
Z-high event polarity flag. Default value: 0
0: Z event was positive g
1: Z event was negative g
This bit read always zero if the a_ffmt_zefe control bit is set to zero
a_ffmt_yhe
Y-high event flag. Default value: 0
0: No event detected
1: Y-high event has been detected
This bit read always zero if the a_ffmt_yefe control bit is set to zero
a_ffmt_yhp
Y-high event polarity flag. Default value: 0
0: Y event detected was positive g
1: Y event was negative g
This bit always reads zero if the a_ffmt_yefe control bit is set to zero
a_ffmt_xhe
X-high event flag. Default value: 0
0: No event detected
1: X-high event has been detected
This bit always reads zero if the a_ffmt_xefe control bit is set to zero
a_ffmt_xhp
X-high event polarity flag. Default value: 0
0: X event was positive g
1: X event was negative g
This bit always reads zero if the a_ffmt_xefe control bit is set to zero
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10.8.3
A_FFMT_THS (0x17), A_FFMT_ THS_X_MSB (0x73), A_FFMT_THS_X_LSB (0x74),
A_FFMT_THS_Y_MSB (0x75), A_FFMT_THS_Y_LSB (0x76), A_FFMT_THS_Z_MSB
(0x77), A_FFMT_THS_Z_LSB (0x78) registers
Freefall/motion detection threshold registers.
Table 78. A_FFMT_THS (0x17) register
a_ffmt_dbcntm
ths[6:0]
0
7’b0000000
Table 79. A_FFMT_THS (0x17) bit descriptions
Field
Description
a_ffmt_dbcntm
The ASIC uses a_ffmt_dbcntm to set the acceleration FFMT debounce counter clear mode independent of the value of
the a_ffmt_ths_xyz_en.
a_ffmt_dbcntm bit configures the way in which the debounce counter is reset when the inertial event of interest is
momentarily not true.
When a_ffmt_dbcntm bit is a logic ‘1’, the debounce counter is cleared to 0 whenever the inertial event of interest is no
longer true (part b, Figure 17) while if the a_ffmt_dbcntm bit is set to logic ‘0’ the debounce counter is decremented by 1
whenever the inertial event of interest in longer true
(part c, Figure 17) until the debounce counter reaches 0 or the inertial event of interest become active.
The decrementing of the debounce counter acts to filter out irregular spurious events which might impede the correct
detection of inertial events.
ths[6:0]
Freefall/motion detection threshold: default value: 7’b0000000. Resolution is fixed at 63 mg/LSB.
Table 80. A_FFMT_THS_X_MSB (0x73) register
a_ffmt_ths_xyz_en
a_ffmt_ths_x[12:6]
0
7’b0000000
Table 81. A_FFMT_THS_X_MSB (0x73) bit descriptions
Field
Description
a_ffmt_ths_xyz_en
For a_ffmt_ths_xyz_en = 0 the ASIC uses the ffmt_ths[6:0] value located in register x17[6:0] as a common threshold
for the X, Y, and Z-axis acceleration detection. The common unsigned 7-bit acceleration threshold has a fixed
resolution of 63 mg/LSB, with a range of 0-127 counts.
For a_ffmt_ths_xyz_en = 1 the ASIC ignores the common 7-bit G_FFMT_THS value located in register x17 when
executing the FFMT function, and the following independent threshold values are used for each axis:
A_FFMT_THS_X_MSB and A_FFMT_THS_X_LSB are used for the X-axis acceleration threshold,
A_FFMT_THS_Y_MSB and A_FFMT_THS_Y_LSB for the Y-axis acceleration threshold,
A_FFMT_THS_Z_MSB and A_FFMT_THS_Z_LSB for the Z-axis acceleration threshold.
The A_FFMT_THS_X/Y/Z thresholds are 13-bit unsigned values that have the same resolution as the accelerometer
output data determined by XYZ_DATA_CFG fs [1:0]. The a_ffmt_ths_xyz_en and a_ffmt_trans_ths_en bits must not
be enabled simultaneously.
a_ffmt_ths_x[12:6]
7-bit MSB of X-axis acceleration threshold
Table 82. A_FFMT_THS_X_LSB (0x74) register
a_ffmt_ths_x[5:0]
—
—
6’b000000
0
0
a_ffmt_ths_y[5:0]
—
—
6’b000000
0
0
Table 83. A_FFMT_THS_Y_MSB (0x75) register
a_ffmt_trans_ths_en
a_ffmt_ths_y[12:6]
0
7’b0000000
Table 84. A_FFMT_THS_Y_LSB (0x76) register
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Table 85. A_FFMT_THS_Z_MSB (0x77) register
—
a_ffmt_ths_z[12:6]
0
7’b0000000
Table 86. A_FFMT_THS_Z_LSB (0x78) register
a_ffmt_ths_z[5:0]
—
—
6’b000000
0
0
+Full Scale
X, Y, Z High-g Region
High-g Positive Threshold
(Motion OR of enabled axes)
Positive
Acceleration
Low-g Threshold
(Freefall - AND of enabled axes)
X, Y, Z Low-g Region
High-g Negative Threshold
(Motion - OR of enabled axes)
X, Y, Z High-g Region
Negative
Acceleration
-Full Scale
Figure 16. A_FFMT_THS high and low-g level
A_FFMT_THS contains the unsigned 7-bit threshold value used by the freefall/motion detection functional block and is used to
detect either low-g (freefall) or high-g (motion) events depending on the setting of G_FFMT_CFG[f_ffmt_oae]. If g_ffmt_oae = 0,
the event is detected when the absolute value of all the enabled axes are below the threshold value. When g_ffmt_oae = 1, the
event is detected when the absolute value of any of the enabled axes is above the threshold value (see Figure 16 for an
illustration of the freefall/motion event detection thresholds). If A_FFMT_THS_X_MSB[a_ffmt_ths_xyz_en] = 1, the behavior is
identical, except that each axis may be programmed with an individual 13-bit threshold (stored in the A_FFMT_X/Y/Z MSB and
LSB registers).
10.8.4
A_FFMT_COUNT (0x18) register
Debounce count register for freefall/motion detection events
This register sets the number of debounce counts for acceleration sample data matching the user-programmed conditions for
either a freefall or motion detection event required before the interrupt is triggered.
Table 87. A_FFMT_COUNT register
a_ffmt_count[7:0]
8’b00000000
Table 88. A_FFMT_COUNT bit description
Field
Description
a_ffmt_count[7:0]
a_ffmt_count defines the minimum number of debounce sample counts required for the detection of a freefall or motion
event. A_FFMT_THS[ffmt_dbcntm] determines the behavior of the counter when the condition of interest is momentarily
not true.
When the internal debounce counter reaches the A_FFMT_COUNT value a freefall/motion event flag is set. The debounce
counter will never increase beyond the A_FFMT_COUNT value. The time step used for the debounce sample count depends on
the ODR chosen (see Table 89).
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Table 89. A_FFMT_COUNT relationship with the ODR
Max time range (s)
ODR (Hz)
Time step (ms)
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
LP
800
0.319
0.319
0.319
0.319
1.25
1.25
1.25
1.25
400
0.638
0.638
0.638
0.638
2.5
2.5
2.5
2.5
200
1.28
1.28
0.638
1.28
5
5
2.5
5
100
2.55
2.55
0.638
2.55
10
10
2.5
10
50
5.1
5.1
0.638
5.1
20
20
2.5
20
12.5
5.1
20.4
0.638
20.4
20
80
2.5
80
6.25
5.1
20.4
0.638
40.8
20
80
2.5
160
1.56
5.1
20.4
0.638
40.8
20
80
2.5
160
For example, an ODR of 100 Hz and a A_ FFMT_COUNT value of 15 would result in minimum debounce response time of
150 ms.
Low-g Event on
all 3-axis
Count Threshold
(a)
FF Counter
EA
Low-g Event on
all 3-axis
a_ffmt_dbcntm = 1
Count Threshold
(b)
Debounce Counter
EA
Low-g Event on
all 3-axis
Count Threshold
Debounce Counter
a_ffmt_dbcntm = 1
(c)
EA
Figure 17. Behavior of the A_FFMT debounce counter in relation to the a_ffmt_dbcntm setting
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10.9
Accelerometer vector-magnitude function
The accelerometer vector-magnitude function is an inertial event detection function available to assist host software algorithms
in detecting motion events.
2
2
2
If ( a_x_out – a_x_ref ) + ( a_y_out – a_y_ref ) + ( a_z_out – a_z_ref ) > A_VECM_THS for a time period greater than the
value stored in A_VECM_CNT, the vector-magnitude change event flag is triggered.
a_x_out, a_y_out, and a_z_out are the current accelerometer output values, and a_x_ref, a_y_ref, and a_z_ref are the reference
values stored internally in the ASIC for each axis or in A_VECM_INIT_X/Y/Z registers if A_VECM_CFG[a_vecm_initm] is set.
Please note that the x_ref, y_ref, and z_ref values are not directly visible to the host application through the register interface.
Please refer to Freescale application note 4458.
10.9.1
A_VECM_CFG (0x5F) register
Table 90. A_VECM_CFG register
—
a_vecm_ele
a_vecm_initm
a_vecm_updm
a_vecm_en
—
—
—
0
0
0
0
0
0
0
0
Table 91. A_VECM_CFG bit descriptions
Field
Description
a_vecm_ele
Control bit a_vecm_ele defines the event latch enable mode. Event latching is disabled for a_vecm_ele = 0. In this
case, the vector-magnitude interrupt flag is in updated real-time and is cleared when the condition for triggering the
interrupt is no longer true. The setting and clearing of the event flag is controlled by the A_VECM_CNT register’s
programmed debounce time.
For a_vecm_ele = 1, the interrupt flag is latched in and held until the host application reads the INT_SOURCE register
(0x0C).
a_vecm_initm
Control bit a_vecm_initm defines how the initial reference values (x_ref, y_ref, and z_ref) are chosen.
For a_vecm_initm = 0 the function uses the current x/y/z accelerometer output data at the time when the vector
magnitude function is enabled.
For a_vecm_initm = 1 the function uses the data from A_VECM_INIT_X/Y/Z registers as the initial reference values.
a_vecm_updm
Control bit a_vecm_updm defines how the reference values are updated once the vector-magnitude function has been
triggered.
For a_vecm_updm = 0, the function updates the reference value with the current x, y, and z accelerometer output data
values.
For a_vecm_updm = 1, the function does not update the reference values when the interrupt is triggered. Instead the
function continues to use the reference values that were loaded when the function was enabled. If both a_vecm_initm
and a_vecm_updm are set to logic ‘1’, the host software can manually update the reference values in real time by
writing to the A_VECM_INITX,Y,Z registers.
a_vecm_en
The accelerometer vector-magnitude function is enabled by setting a_vecm_en = 1, and disabled by clearing this bit
(default). The reference values are loaded with either the current X/Y/Z acceleration values or the values stored in the
A_VECM_INIT_X/Y/Z registers, depending on the state of the a_vecm_initm bit.
Note: The vector-magnitude function will only perform correctly up to a maximum ODR of 400 Hz.
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10.9.2
A_VECM_THS_MSB (0x60) register
Table 92. A_VECM_THS_MSB register
a_vecm_dbcntm
—
—
a_vecm_ths[12:8]
0
0
0
5’b00000
Table 93. A_VECM_THS_MSB bit descriptions
Field
Description
a_vecm_dbcntm
Control bit a_vecm_dbcntm defines how the debounce timer is reset when the condition for triggering the interrupt is
no longer true.
When a_vecm_dbcntm = 0 the debounce counter is decremented by 1 when the vector-magnitude result is below the
programmed threshold value.
When a_vecm_dbcntm = 1 the debounce counter is cleared when the vector-magnitude result is below the
programmed threshold value.
a_vecm_ths[12:8]
Five MSBs of the 13-bit unsigned A_VECM_THS value. The resolution is equal to the selected accelerometer
resolution set in XYZ_DATA_CFG[fs]
10.9.3
A_VECM_THS_LSB (0x61) register
Table 94. A_VECM_THS_LSB register
a_vecm_ths[7:0]
8’b00000000
10.9.4
A_VECM_CNT (0x62) register
Table 95. A_VECM_CNT register
a_vecm_cnt[7:0]
8’b00000000
Table 96. A_VECM_CNT bit description
Field
a_vecm_cnt[7:0]
Description
Vector-magnitude function debounce count value.
The debounce timer period is determined by the ODR selected in CTRL_REG1; it is equal to the number indicated in
A_VECM_CNT register times 1/ODR. For example, a value of 16 in A_VECM_CNT with an ODR setting of 400 Hz will result in
a debounce period of 40 ms.
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10.9.5
A_VECM_INITX_MSB (0x63) register
Table 97. A_VECM_INITX_MSB register
—
—
a_vecm_initx[13:8]
0
0
6’b000000
Table 98. A_VECM_INITX_MSB bit description
Field
Description
Most significant 6 bits of the signed 14-bit initial X-axis value to be used as ref_x when A_VECM_CFG[a_vecm_initm] = 1.
a_vecm_initx[13:8]
The resolution is determined by the settings made in XYZ_DATA_CFG[fs], and is equal to the accelerometer resolution.
10.9.6
A_VECM_INITX_LSB (0x64) register
Table 99. A_VECM_INITX_LSB register
a_vecm_initx[7:0]
8’b00000000
Table 100. A_VECM_INITX_LSB bit description
Field
Description
a_vecm_initx[7:0]
LSB of the signed 14-bit initial X-axis value to be used as ref_x when A_VECM_CFG[a_vecm_initm] = 1. The
resolution is determined by the settings made in XYZ_DATA_CFG[fs], and is equal to the accelerometer resolution.
10.9.7
A_VECM_INITY_MSB (0x65) register
Table 101. A_VECM_INITY_MSB register
—
—
a_vecm_inity[13:8]
0
0
6’b000000
Table 102. A_VECM_INITY_MSB bit description
Field
Description
a_vecm_inity[13:8]
Most significant 6 bits of the signed 14-bit initial Y-axis value to be used as ref_y when A_VECM_CFG[a_vecm_initm]
= 1. The resolution is determined by the settings made in XYZ_DATA_CFG[fs], and is equal to the accelerometer
resolution.
10.9.8
A_VECM_INITY_LSB (0x66) register
Table 103. A_VECM_INITY_LSB register
a_vecm_inity[7:0]
Table 104. A_VECM_INITY_LSB bit description
Field
Description
a_vecm_inity[7:0]
LSB of the signed 14-bit initial Y-axis value to be used as ref_y when A_VECM_CFG[a_vecm_initm] = 1. The resolution
is determined by the settings made in XYZ_DATA_CFG[fs], and is equal to the accelerometer resolution.
10.9.9
A_VECM_INITZ_MSB (0x67) register
Table 105. A_VECM_INITZ_MSB register
—
—
a_vecm_initz[13:8]
0
0
6’b000000
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Table 106. A_VECM_INITZ_MSB bit description
Field
Description
a_vecm_initz[13:8]
Most significant 6 bits of the signed 14-bit initial Z-axis value to be used as ref_z when A_VECM_CFG[a_vecm_initm]
= 1. The resolution is determined by the settings made in XYZ_DATA_CFG[fs], and is equal to the accelerometer
resolution.
10.9.10 A_VECM_INITZ_LSB (0x68) register
Table 107. A_VECM_INITZ_LSB register
a_vecm_initz[7:0]
8’b00000000
Table 108. A_VECM_INITZ_LSB bit description
Field
Description
a_vecm_initz[7:0]
LSB of the signed 14-bit initial Z-axis value to be used as ref_z when A_VECM_CFG[a_vecm_initm] = 1. The
resolution is determined by the settings made in XYZ_DATA_CFG[fs], and is equal to the accelerometer resolution.
10.10
Transient (AC) acceleration detection
The transient detection function is similar to the freefall/motion detection function with the exception that a high-pass filter can be
used to eliminate the DC offset from the acceleration data. There is an option to disable the high-pass filter, which causes the
transient detection function to work in a similar manner to the motion detection function.
The transient detection function can be configured to signal an interrupt when the high-pass filtered acceleration delta values for
any of the enabled axes exceeds the threshold programmed in TRANSIENT_THS for the debounce time programmed in
TRANSIENT_COUNT. For more information on how to use and configure the transient detection function please refer to
Freescale application note AN4461.
10.10.1 TRANSIENT_CFG (0x1D) register
Table 109. TRANSIENT_ CFG register
—
—
—
tran_ele
tran_zefe
tran_yefe
tran_xefe
tran_hpf_byp
0
0
0
0
0
0
0
0
Table 110. TRANSIENT_ CFG bit descriptions
Field
Description
tran_ele
Transient event flag latch enable. Default value: 0
0: Event flag latch disabled: the transient interrupt flag reflects the real-time status of the function.
1: Event flag latch enabled: the transient interrupt event flag is latched and a read of the TRANSIENT_SRC register is
required to clear the event flag.
tran_zefe
Z-axis transient event flag enable. Default value: 0
0: Z-axis event detection disabled
1: Z-axis event detection enabled. Raise event flag on Z-axis acceleration value greater than threshold.
tran_yefe
Y-axis transient event flag enable. Default value: 0
0: Y-axis event detection disabled
1: Y-axis event detection enabled. Raise event flag on Y-axis acceleration value greater than threshold.
tran_xefe
X-axis transient event flag enable. Default value: 0
0: X-axis event detection disabled
1: X-axis event detection enabled. Raise event flag on X-axis acceleration value greater than threshold.
tran_hpf_byp
Transient function high-pass filter bypass. Default value: 0
0: High-pass filter is applied to accelerometer data input to the transient function.
1: High-pass filter is not applied to accelerometer data input to the transient function.
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10.10.2 TRANSIENT_SRC (0x1E) register
Transient event flag source register. This register provides the event status of the enabled axes and polarity (directional)
information.
Table 111. TRANSIENT_ CFG register
—
tran_ea
tran_zef
tran_zpol
tran_yef
tran_ypol
tran_xef
trans_xpol
0
0
0
0
0
0
0
0
Table 112. TRANSIENT_SRC bit descriptions
Field
Description
tran_ea
Transient event active flag. Default value: 0
0: No transient event active flag has been asserted.
1: One or more transient event active flags has been asserted.
tran_zef
Z-axis transient event active flag. Default value: 0
0: Z-axis event flag is not active.
1: Z-axis event flag is active; Z-axis acceleration has exceeded the programmed threshold for the debounce time specified
in TRANS_COUNT.
tran_zpol
Z-axis event flag polarity.
0: Z-axis event was above positive threshold value.
1: Z-axis event was below negative threshold value.
tran_yef
Y-axis transient event active flag. Default value: 0
0: Y-axis event flag is not active.
1: Y-axis event flag is active; Y-axis acceleration has exceeded the programmed threshold for the debounce time specified
in TRANS_COUNT.
tran_ypol
Y-axis event flag polarity.
0: Y-axis event was above positive threshold value.
1: Y-axis event was below negative threshold value.
tran_xef
X-axis transient event active flag. Default value: 0
0: X-axis event flag is not active.
1: X-axis event flag is active; X-axis acceleration has exceeded the programmed threshold for the debounce time specified
in TRANS_COUNT.
tran_xpol
X-axis event flag polarity.
0: X-axis event was above positive threshold value.
1: X-axis event was below negative threshold value.
When TRANSIENT_CFG[tran_ele] = 1, the TRANSIENT_SRC event flag(s) and polarity bits are latched when the interrupt event
is triggered, allowing the host application to determine which event flag(s) originally triggered the interrupt. When
TRANSIENT_CFG[tran_ele] = 0, events which occur after the event that originally triggered the interrupt will update the flag and
polarity bits, but once set, the flags can only be cleared by reading the TRANSIENT_SRC register.
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10.10.3 TRANSIENT_THS (0x1F) register
The TRANSIENT_THS register determines the debounce counter behavior and also sets the transient event detection
threshold.It is possible to use A_FFMT_THS_X/Y/Z MSB and LSB registers to set transient acceleration thresholds for individual
axes using the a_ffmt_trans_ths_en bit in A_FFMT_THS_Y_MSB register.
Table 113. TRANSIENT_THS register
tr_dbcntm
tr_ths[6:0]
0
7’b0000000
Table 114. TRANSIENT_THS bit descriptions
Field
Description
tr_dbcntm
Debounce counter mode selection.
0: Decrements debounce counter when the transient event condition is not true during the current ODR period.
1: Clears debounce counter when the transient event condition is not true during the current ODR period.
tr_ths[6:0]
Transient event threshold. This register has a resolution of 63 mg/LSB regardless of the full-scale range setting made in
XYZ_DATA_CFG[fs]. If CTRL_REG1[lnoise] = 1, the maximum acceleration measurement range is ±4 g.
The tr_ths[6:0] value is a 7-bit unsigned number, with a fixed resolution of 63 mg/LSB corresponding to a ±8 g measurement
range. The resolution does not change with the full-scale range setting made in XYZ_DATA_CFG[fs]. If CTRL_REG1[lnoise] = 1,
the measurement range is fixed at ±4 g, regardless of the settings made in XYZ_DATA_CFG.
10.10.4 TRANSIENT_COUNT (0x20) register
The TRANSIENT_COUNT register sets the minimum number of debounce counts needed to trigger the transient event interrupt
flag when the measured acceleration value exceeds the threshold set in TRANSIENT_THS for any of the enabled axes.
Table 115. TRANSIENT_COUNT register
tr_count[7:0]
8’b00000000
Table 116. TRANSIENT_COUNT bit description
Field
tr_count[7:0)
Description
Transient function debounce count value.
The time step for the transient detection debounce counter is set by the value of the system ODR and power mode as shown in
Table 117.
Table 117. TRANSIENT_COUNT relationship with the ODR
Max time range (s)
ODR (Hz)
Time step (ms)
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
Low power
800
0.319
0.319
0.319
0.319
1.25
1.25
1.25
1.25
400
0.638
0.638
0.638
0.638
2.5
2.5
2.5
2.5
200
1.28
1.28
0.638
1.28
5
5
2.5
5
100
2.55
2.55
0.638
2.55
10
10
2.5
10
50
5.1
5.1
0.638
5.1
20
20
2.5
20
12.5
5.1
20.4
0.638
20.4
20
80
2.5
80
6.25
5.1
20.4
0.638
40.8
20
80
2.5
160
1.56
5.1
20.4
0.638
40.8
20
80
2.5
160
An ODR of 100 Hz and a TRANSIENT_COUNT value of 15, when accelerometer OSR is set to normal using CTRL_REG2,
would result in minimum debounce response time of 150 ms.
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10.11
Pulse detection
10.11.1 PULSE_CFG (0x21) register
This register configures the pulse event detection function.
Table 118. PULSE_CFG register
pls_dpa
pls_ele
pls_zdpefe
pls_zspefe
pls_ydpefe
pls_yspefe
pls_xdpefe
pls_xspefe
0
0
0
0
0
0
0
0
Table 119. PULSE_CFG bit descriptions
Field
Description
pls_dpa
Double-pulse abort.
0: Double-pulse detection is not aborted if the start of a pulse is detected during the time period specified by the
PULSE_LTCY register.
1: Setting the pls_dpa bit momentarily suspends the double-tap detection if the start of a pulse is detected during the
time period specified by the PULSE_LTCY register and the pulse ends before the end of the time period specified by
the PULSE_LTCY register.
pls_ele
Pulse event flag latch enable. When enabled, a read of the PULSE_SRC register is needed to clear the event flag.
0: Event flag latch disabled
1: Event flag latch enabled
pls_zdpefe
Event flag enable on double-pulse event on Z-axis.
0: Event detection disabled
1: Raise event flag on detection of double-pulse event on Z-axis
pls_zspefe
Event flag enable on single-pulse event on Z-axis.
0: Event detection disabled
1: Raise event flag on detection of single-pulse event on Z-axis
pls_ydpefe
Event flag enable on double-pulse event on Y-axis.
0: Event detection disabled
1: Raise event flag on detection of double-pulse event on Y-axis
pls_yspefe
Event flag enable on single-pulse event on Y-axis.
0: Event detection disabled
1: Raise event flag on detection of single-pulse event on Z-axis.
pls_xdpefe
Event flag enable on double-pulse event on X-axis.
0: Event detection disabled
1: Raise event flag on detection of double-pulse event on X-axis.
pls_xspefe
Event flag enable on single-pulse event on X-axis.
0: Event detection disabled
1: Raise event flag on detection of single-pulse event on X-axis.
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10.11.2 PULSE_SRC (0x22) register
This register indicates the status bits for the pulse detection function.
Table 120. PULSE_SRC register
pls_src_ea
pls_src_axz
pls_src_axy
pls_src_axx
pls_src_dpe
pls_src_polz
pls_src_poly
pls_src_polx
Table 121. PULSE_SRC bit descriptions
Field
Description
pls_src_ea
Event active flag.
0: No interrupt has been generated
1: One or more interrupt events have been generated
pls_src_axz
Z-axis event flag.
0: No interrupt.
1: Z-axis event has occurred
pls_src_axy
Y-axis event flag.
0: No interrupt.
1: Y-axis event has occurred
pls_src_axx
X-axis event flag.
0: No interrupt.
1: X-axis event has occurred.
pls_src_dpe
Double pulse on first event.
0: Single-pulse event triggered interrupt.
1: Double-pulse event triggered interrupt.
pls_src_polz
Pulse polarity of Z-axis event.
0: Pulse event that triggered interrupt was positive.
1: Pulse event that triggered interrupt was negative.
pls_src_poly
Pulse polarity of Y-axis event.
0: Pulse event that triggered interrupt was positive.
1: Pulse event that triggered interrupt was negative.
pls_src_polx
Pulse polarity of X-axis event.
0: Pulse event that triggered interrupt was positive.
1: Pulse event that triggered interrupt was negative.
10.11.3 PULSE_THSX (0x23) register
Table 122. PULSE_THSX register
—
pls_thsx[6:0]
0
7’b0000000
Table 123. PULSE_THSX bit description
Field
pls_thsx[6:0]
Description
Pulse threshold for X-axis.
The PULSE_THSX, PULSE_THSY and PULSE_THSZ registers define the thresholds used by the system to start the pulseevent detection procedure. Threshold values for each axis are unsigned 7-bit numbers with a fixed resolution of 0.063 g/LSB,
corresponding to an 8 g acceleration full-scale range. The full-scale range is fixed at 8 g for the pulse detection function,
regardless of the settings made in XYZ_DATA_CFG[fs].
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10.11.4 PULSE_THSY (0x24) register
Table 124. PULSE_THSY register
—
pls_thsy[6:0]
0
7’b0000000
Table 125. PULSE_THSY bit description
Field
pls_thsy[6:0]
Description
Pulse threshold for Y-axis.
10.11.5 PULSE_THSZ (0x25) register
Table 126. PULSE_THSZ register
—
pls_thsz[6:0]
0
7’b0000000
Table 127. PULSE_THSZ bit description
Field
pls_thsz[6:0]
Description
Pulse threshold for Z-axis.
10.11.6 PULSE_TMLT (0x26) register
Table 128. PULSE_TMLT register
pls_tmlt[7:0]
8’b00000000
Table 129. PULSE_TMLT bit description
Field
pls_tmlt[7:0]
Description
pls_tmlt[7:0] defines the maximum time interval that can elapse between the start of the acceleration on the selected
channel exceeding the specified threshold and the end when the channel acceleration goes back below the specified
threshold.
Minimum time step for the pulse-time limit is defined in Tables 130 and 131. Maximum time for a given ODR is “Minimum time
step x 255”.
Table 130. Time step for PULSE_TMLT with HP_FILTER_CUTOFF[pls_hpf_en] = 1
Max time range (s)
ODR (Hz)
Time step (ms)
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
Low power
800
0.319
0.319
0.319
0.319
1.25
1.25
1.25
1.25
400
0.638
0.638
0.638
0.638
2.5
2.5
2.5
2.5
200
1.28
1.28
0.638
1.28
5
5
2.5
5
100
2.55
2.55
0.638
2.55
10
10
2.5
10
50
5.1
5.1
0.638
5.1
20
20
2.5
20
12.5
5.1
20.4
0.638
20.4
20
80
2.5
80
6.25
5.1
20.4
0.638
40.8
20
80
2.5
160
1.56
5.1
20.4
0.638
40.8
20
80
2.5
160
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Table 131. Time step for PULSE_TMLT with HP_FILTER_CUTOFF[pls_hpf_en] = 0
Max time range (s)
ODR (Hz)
Time step (ms)
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
Low power
800
0.159
0.159
0.159
0.159
0.625
0.625
0.625
0.625
400
0.159
0.159
0.159
0.319
0.625
0.625
0.625
1.25
200
0.319
0.319
0.159
0.638
1.25
1.25
0.625
2.5
100
0.638
0.638
0.159
1.28
2.5
2.5
0.625
5
50
1.28
1.28
0.159
2.55
5
5
0.625
10
12.5
1.28
5.1
0.159
10.2
5
20
0.625
40
6.25
1.28
5.1
0.159
10.2
5
20
0.625
40
1.56
1.28
5.1
0.159
10.2
5
20
0.625
40
Therefore an ODR setting of 400 Hz, when accelerometer OSR is set to normal using CTRL_REG2, would result in a maximum
pulse-time limit of (0.625 ms * 255) = 159 ms.
10.11.7 PULSE_LTCY (0x27) register
Table 132. PULSE_LTCY register
pls_ltcy[7:0]
8’b00000000
Table 133. PULSE_LTCY bit description
Field
Description
pls_ltcy[7:0]
pls_ltcy[7:0] defines the time interval that starts after the first pulse detection where the pulse-detection function ignores
the start of a new pulse.
Minimum time step for the pulse latency is defined in Tables 134 and 135. Maximum time is “(time step @ ODR and power mode)
x 255”.
Table 134. Time step for PULSE_LTCY with HP_FILTER_CUTOFF[pls_hpf_en] = 1
Max time range (s)
ODR (Hz)
Normal
LPLN
High
resolution
Time step (ms)
Low power
Normal
LPLN
High
resolution
Low power
800
0.638
0.638
0.638
0.638
2.5
2.5
2.5
2.5
400
1.276
1.276
1.276
1.276
5
5
5
5
200
2.56
2.56
1.276
2.56
10
10
5
10
100
5.1
5.1
1.276
5.1
20
20
5
20
50
10.2
10.2
1.276
10.2
40
40
5
40
12.5
10.2
40.8
1.276
40.8
40
160
5
160
6.25
10.2
40.8
1.276
81.6
40
160
5
320
1.56
10.2
40.8
1.276
81.6
40
160
5
320
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Table 135. Time step for PULSE_LTCY with HP_FILTER_CUTOFF[pls_hpf_en] = 0
Max time range (s)
ODR (Hz)
Time step (ms)
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
Low power
800
0.318
0.318
0.318
0.318
1.25
1.25
1.25
1.25
400
0.318
0.318
0.318
0.638
1.25
1.25
1.25
2.5
200
0.638
0.638
0.318
1.276
2.5
2.5
1.25
5
100
1.276
1.276
0.318
2.56
5
5
1.25
10
50
2.56
2.56
0.318
5.1
10
10
1.25
20
12.5
2.56
10.2
0.318
20.4
10
40
1.25
80
6.25
2.56
10.2
0.318
20.4
10
40
1.25
80
1.56
2.56
10.2
0.318
20.4
10
40
1.25
80
10.11.8 PULSE_WIND (0x28) register
Table 136. PULSE_WIND register
pls_wind[7:0]
8’b00000000
Table 137. PULSE_WIND bit description
Field
Description
pls_wind[7:0]
pls_wind[7:0] defines the maximum interval of time that can elapse after the end of the latency interval in
which the start of the second pulse event must be detected provided the device has been configured for
double pulse detection. The detected second pulse width must be shorter than the time limit constraint
specified by the PULSE_TMLT register, but the end of the double pulse need not finish within the time
specified by the PULSE_WIND register.
The time step for the pulse-window counter varies with the selected ODR and power modes as defined in Tables 138 and 139.
The maximum time value is equal to (time step @ ODR and power mode) x 255.
Table 138. Time step for PULSE_WIND with HP_FILTER_CUTOFF[pls_hpf_en] = 1
Max time range (s)
ODR (Hz)
Normal
LPLN
High
resolution
Time step (ms)
Low power
Normal
LPLN
High
resolution
Low power
800
0.638
0.638
0.638
0.638
2.5
2.5
2.5
2.5
400
1.276
1.276
1.276
1.276
5
5
5
5
200
2.56
2.56
1.276
2.56
10
10
5
10
100
5.1
5.1
1.276
5.1
20
20
5
20
50
10.2
10.2
1.276
10.2
40
40
5
40
12.5
10.2
40.8
1.276
40.8
40
160
5
160
6.25
10.2
40.8
1.276
81.6
40
160
5
320
1.56
10.2
40.8
1.276
81.6
40
160
5
320
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Table 139. Time step for PULSE_WIND with HP_FILTER_CUTOFF[pls_hpf_en] = 0
Max time range (s)
ODR (Hz)
Time step (ms)
Normal
LPLN
High
resolution
Low power
Normal
LPLN
High
resolution
Low power
800
0.318
0.318
0.318
0.318
1.25
1.25
1.25
1.25
400
0.318
0.318
0.318
0.638
1.25
1.25
1.25
2.5
200
0.638
0.638
0.318
1.276
2.5
2.5
1.25
5
100
1.276
1.276
0.318
2.56
5
5
1.25
10
50
2.56
2.56
0.318
5.1
10
10
1.25
20
12.5
2.56
10.2
0.318
20.4
10
40
1.25
80
6.25
2.56
10.2
0.318
20.4
10
40
1.25
80
1.56
2.56
10.2
0.318
20.4
10
40
1.25
80
10.12
Offset correction
The 8-bit 2’s complement offset correction registers are used to remove the sensor zero g offset on the X, Y, and Z axes after
device board mount. The resolution of the offset registers is 2 mg per LSB, with an effective offset adjustment range of -256 mg
to +254 mg for each axis.
For more information on how to calibrate the 0 g offset, please refer to Freescale application note AN4069.
10.12.1 OFF_X (0x2F) register
Table 140. OFF_X register
off_x[7:0]
8’b00000000
Table 141. OFF_X bit description
Field
off_x[7:0]
Description
X-axis offset correction value expressed as an 8-bit 2's complement number.
10.12.2 OFF_Y (0x30) register
Table 142. OFF_Y register
off_y[7:0]
8’b00000000
Table 143. OFF_Y bit description
Field
off_y[7:0]
Description
Y-axis offset correction value expressed as an 8-bit 2's complement number.
10.12.3 OFF_Z (0x31) register
Table 144. OFF_Z register
off_z[7:0]
8’b00000000
Table 145. OFF_Z bit description
Field
off_z[7:0]
Description
Z-axis offset correction value expressed as an 8-bit 2's complement number.
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Mounting Guidelines for the Quad Flat No-Lead (QFN) Package
Printed Circuit Board (PCB) layout is a critical portion of the total design. The footprint for the surface mount packages must be
the correct size to ensure proper solder connection interface between the PCB and the package. With the correct footprint, the
packages will self-align when subjected to a solder reflow process.
These guidelines are for soldering and mounting the Quad Flat No-Lead (QFN) package inertial sensors to PCBs. The purpose
is to minimize the stress on the package after board mounting. The FXLS8471Q uses the QFN package platform. This section
describes suggested methods of soldering these devices to the PCB for consumer applications.
Freescale application note AN1902, “Quad Flat Pack No-Lead (QFN) Micro Dual Flat Pack No-Lead (DFN)” discusses the QFN
package used by the FXLS8471Q, PCB design guidelines for using QFN packages and temperature profiles for reflow soldering.
11.1
Overview of soldering considerations
Information provided here is based on experiments executed on QFN devices. As they cannot represent exact conditions present
at a customer site, the information provided herein should be used for guidance only and further process and design optimizations
are recommended to develop an application specific solution. It should be noted that with the proper PCB footprint and solder
stencil designs, the package will self-align during the solder reflow process.
11.2
Halogen content
This package is designed to be Halogen Free, exceeding most industry and customer standards. Halogen Free means that no
homogeneous material within the assembled package will contain chlorine (Cl) in excess of 700 ppm or 0.07% weight/weight or
bromine (Br) in excess of 900 ppm or 0.09% weight/weight.
11.3
PCB mounting recommendations
1.
2.
3.
4.
5.
6.
7.
The PCB land should be designed with Non-Solder Mask Defined (NSMD) as shown in Figure 18 and Figure 19.
No additional via pattern underneath package.
PCB land pad is 0.8 mm by 0.3 mm as shown in Figure 18 and Figure 19.
Solder mask opening = PCB land pad edge + 0.113 mm larger all around.
Stencil opening = PCB land pad -0.015 mm smaller all around = 0.77 mm by 0.27 mm.
Stencil thickness is 100 or 125 μm.
Do not place any components or vias at a distance less than 2 mm from the package land area. This may cause
additional package stress if it is too close to the package land area.
8. Signal traces connected to pads should be as symmetric as possible. Put dummy traces on the NC pads in order to
have same length of exposed trace for all pads.
9. Use a standard pick and place process and equipment. Do not use a hand soldering process.
10. Do not use a screw down or stacking to fix the PCB into an enclosure as this could bend the PCB, putting stress on the
package.
11. The PCB should be rated for the multiple lead-free reflow condition with max 260°C temperature.
12. No copper traces on top layer of PCB under the package. This will cause planarity issues with board mount. Freescale
QFN sensors are compliant with Restrictions on Hazardous Substances (RoHS), having halide-free molding
compound (green) and lead-free terminations. These terminations are compatible with tin-lead (Sn-Pb) as well as tinsilver-copper (Sn-Ag-Cu) solder paste soldering processes. Reflow profiles applicable to those processes can be used
successfully for soldering the devices.
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PCB Land Pattern & Stencil
Package Footprint
0.567 mmxx0.25mm
0.25 mm
0.467mm
Package
footprint
Solder mask opening
= PCB land pad edge
+ 0.113mm larger all
around
PCB land pad =
0.8mm x 0.3mm
No copper in this area
Stencil opening = PCB land
pad -0.015mm smaller all
around
= 0.77mm x 0.27mm
Figure 18. Recommended PCB land pattern, solder mask, and stencil opening near package footprint
Figure 19. Detailed dimensions
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Package Thermal Characteristics
Table 146. Thermal resistance data
Rating
Description
Junction-to-ambient, natural convection(1)(2)
Single-layer board
Junction-to-ambient, natural convection(1)(3)
Four-layer board (two signals, two planes)
Junction-to-board(4)
Junction-to-case (top)(5)
Junction-to-package (top)
(6)
Natural convection
Symbol
RθJA
Value
163
Unit
°C/W
70
RθJB
33
°C/W
RθJCTop
84
°C/W
ΨJT
6
°C/W
1. Junction temperature is a function of die size, on-chip power dissipation, package thermal resistance, mounting site (board) temperature,
ambient temperature, air flow, power dissipation of other components on the board, and board thermal resistance.
2. Per JEDEC JESD51-2 with the single-layer board (JESD51-3) horizontal.
3. Per JEDEC JESD51-6 with the board (JESD51-7) horizontal.
4. Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is measured on the top surface
of the board near the package.
5. Thermal resistance between the die and the case top surface as measured by the cold plate method (MIL SPEC-883 Method 1012.1).
6. Thermal characterization parameter indicating the temperature difference between package top and the junction temperature per JEDEC
JESD51-2. When Greek letters are not available, the thermal characterization parameter is written as Psi-JT.
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13
Package
This drawing is located at http://cache.freescale.com/files/shared/doc/package_info/98ASA00063D.pdf.
A
B
D
E
F
G
CASE 2077-02
ISSUE A
16-LEAD QFN
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C
C1
CASE 2077-02
ISSUE A
16-LEAD QFN
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Table 147. Package dimensions (mm)
Symbol
A
Min
Typ
Max
Package width
Description
2.9
3
3.1
B
Package length
2.9
3
3.1
C
Package thickness
0.9
0.98
1
C1
Lead finger (pad) seating height
0
—
0.05
D
Lead finger (pad) width
0.18
0.25
0.30
E
Lead length
0.367
0.467
0.567
F
Lead finger-finger (pad-pad) pitch
—
0.5
—
G
Package edge to inner edge of lead
0.467
0.567
0.667
CASE 2077-02
ISSUE A
16-LEAD QFN
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Appendix A
A.1
A.1.1
Errata
SPI Mode Soft-reset using CTRL_REG2 (0x2B), bit 6
Description:
Following a soft-reset command, issued by setting CTRL_REG2[rst] = 1, certain device-specific parameters do not get updated
correctly from NVM, causing inaccurate data output and incorrect WHOAMI (0x0D) register content. This behavior happens only
in SPI mode. In I2C mode the device works as advertised.
Workaround:
Avoid using soft-reset in SPI mode by alternately utilizing the hardware RESET pin.
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14
Revision History
Table 148. Revision history
Revision
number
Revision
date
1.0
8/2013
• Initial data sheet.
1.1
8/2013
• Global update: “counts/g” changed to “LSB/g” throughout document.
• Table 2: Updated Min values for Self-Test output change, X, Y, and Z from +249, +335, and +1680 to +192, +270,
and +1275 respectively.
• Appendix A.1.1: Corrected register name in Description paragraph.
1.2
11/2014
• Added Ordering Information table on page 2.
1.3
01/2015
• Added callouts to the package drawing and dimension table following package drawing.
Description of changes
1.4
03/2015
• Table 147: Added Typ dimensions for Symbol C and E.
1.5
06/2015
• Added G callout to package drawing and dimension table following package drawing.
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© 2013-2015 Freescale Semiconductor, Inc.
Document Number: FXLS8471Q
Rev. 1.5
06/2015