PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Product Description
The KXTI9 is a tri-axis +/-2g, +/-4g or +/-8g silicon micromachined
accelerometer with integrated orientation, tap/double tap, and
activity detecting algorithms. The sense element is fabricated using
Kionix’s proprietary plasma micromachining process technology.
Acceleration sensing is based on the principle of a differential
capacitance arising from acceleration-induced motion of the sense
element, which further utilizes common mode cancellation to
decrease errors from process variation, temperature, and
environmental stress. The sense element is hermetically sealed at
the wafer level by bonding a second silicon lid wafer to the device
using a glass frit. A separate ASIC device packaged with the sense
element provides signal conditioning, and intelligent userprogrammable application algorithms.
The accelerometer is
delivered in a 3 x 3 x 0.9 mm LGA plastic package operating from a
1.8 – 3.6V DC supply. Voltage regulators are used to maintain
constant internal operating voltages over the range of input supply voltages. This results in stable
operating characteristics over the range of input supply voltages and virtually undetectable ratiometric
error. I2C digital protocol is used to communicate with the chip to configure and check for updates to
the orientation, Directional TapTM detection and activity monitoring algorithms.
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Page 1 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Functional Diagram
X
Sensor
Y
Sensor
Charge
Amp
Z
Sensor
Temp
Sensor
A/D
Digital
Filter
Vdd 5
2
I C
Digital Engine
IO Vdd 1
GND 4
6
8
9
10
RSVD DNC SCL SDA
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7
INT
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Page 2 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Product Specifications
Table 1. Mechanical
(specifications are for operation at 2.6V and T = 25C unless stated otherwise)
Parameters
Units
Min
Typical
Operating Temperature Range
Zero-g Offset
Zero-g Offset Variation from RT over Temp.
ºC
mg
Sensitivity (8-bit)
1
1
GSEL1=0, GSEL0=1 (± 4g)
GSEL1=1, GSEL0=0 (± 8g)
GSEL1=0, GSEL0=0 (± 2g)
GSEL1=0, GSEL0=1 (± 4g)
GSEL1=1, GSEL0=0 (± 8g)
Sensitivity Variation from RT over Temp.
Self Test Output change on Activation
Mechanical Resonance (-3dB)
Non-Linearity
Cross Axis Sensitivity
Notes:
2
counts/g
counts/g
Max
85
±125
988
±25
0.7 (xy)
0.4 (z)
1024
494
512
530
247
61
30
15
256
64
32
16
0.01 (xy)
0.03 (z)
0.7 (xy)
0.5 (z)
3500 (xy)
1800 (z)
0.6
2
265
67
34
17
mg/ºC
GSEL1=0, GSEL0=0 (± 2g)
Sensitivity (12-bit)
-40
-
%/ºC
g
Hz
% of FS
%
1060
2
1. Resolution and acceleration ranges are user selectable via I C.
2. Resonance as defined by the dampened mechanical sensor.
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Page 3 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Table 2. Electrical
(specifications are for operation at 2.6V and T = 25C unless stated otherwise)
Parameters
Units
Min
Typical
Max
Supply Voltage (Vdd) Operating
I/O Pads Supply Voltage (VIO)
All On (RES = 1)
Directional Tap™
(RES = 0, ODR = 400Hz)
Current Consumption
Low Power
(RES = 0, ODR ≤ 25Hz)
Standby
1
Output Low Voltage (Vio < 2V)
1
Output Low Voltage (Vio > 2V)
Output High Voltage
Input Low Voltage
Input High Voltage
Input Pull-down Current
RES = 0
RES = 1, ODR = 12.5Hz
RES = 1, ODR = 25 Hz
RES = 1, ODR = 50Hz
2
Start Up Time
RES = 1, ODR = 100Hz
RES = 1, ODR = 200Hz
RES = 1, ODR = 400Hz
RES = 1, ODR = 800Hz
3
Power Up Time
2
I C Communication Rate
4
Output Data Rate (ODR)
RES = 0
5
Bandwidth (-3dB)
RES = 1
V
V
1.71
1.7
2.6
3.6
Vdd
325
165
A
100
V
V
V
V
V
0.8 * Vio
0.8 * Vio
A
ms
ms
kHz
Hz
kHz
Hz
10
0
0.050
81
41
21
11
6
4
2.5
10
0.2 * Vio
0.4
0.2 * Vio
-
400
12.5
50
800
1.59
ODR/2
Notes:
2
1. For I C communication, this assumes a minimum 1.5k pull-up resistor on SCL and
SDA pins.
2. Start up time is from PC1 set to valid outputs.
3. Power up time is from Vdd valid to device boot completion.
2
4. User selectable through I C.
5. User selectable and dependant on ODR and RES.
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Page 4 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Table 3. Environmental
Units
Min
Typical
Max
Supply Voltage (Vdd) Absolute Limits
Operating Temperature Range
Storage Temperature Range
Parameters
V
ºC
ºC
-0.5
-40
-55
-
Mech. Shock (powered and unpowered)
g
-
-
ESD
V
-
-
3.63
85
150
5000 for 0.5ms
10000 for 0.2ms
2000
HBM
Caution: ESD Sensitive and Mechanical Shock Sensitive Component, improper handling
can cause permanent damage to the device.
This product conforms to Directive 2002/95/EC of the European Parliament and of the
Council of the European Union (RoHS). Specifically, this product does not contain lead,
mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), or
polybrominated diphenyl ethers (PBDE) above the maximum concentration values (MCV) by
weight in any of its homogenous materials. Homogenous materials are "of uniform
composition throughout."
HF
This product is halogen-free per IEC 61249-2-21. Specifically, the materials used in this
product contain a maximum total halogen content of 1500 ppm with less than 900-ppm
bromine and less than 900-ppm chlorine.
Soldering
Soldering recommendations are available upon request or from www.kionix.com.
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Page 5 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Application Schematic
SDA
10
IO Vdd
1
9
2
8
SCL
KXTI9
C2
3
7
4
6
INT
5
C1
Vdd
Table 4. KXTI9 Pin Descriptions
Pin
Name
Description
DNC
DNC
The power supply input for the digital communication bus. Optionally decouple this pin to ground with
a 0.1uF ceramic capacitor.
Reserved – Do Not Connect
Reserved – Do Not Connect
4
GND
Ground
5
6
7
8
9
10
Vdd
RSVD
INT
DNC
SCL
SDA
The power supply input. Decouple this pin to ground with a 0.1uF ceramic capacitor.
Reserved – Float or connect to IO Vdd
Physical Interrupt
Reserved – Do Not Connect
I2C Serial Clock
I2C Serial Data
1
2
3
IO Vdd
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Page 6 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Test Specifications
!
Special Characteristics:
These characteristics have been identified as being critical to the customer. Every part is tested to
verify its conformance to specification prior to shipment.
Table 5. Test Specifications
Parameter
Zero-g Offset @ RT
Sensitivity @ RT
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tel: 607-257-1080 – fax:607-257-1146
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Specification
0 +/- 128 counts
1024 +/- 35.8 counts/g
Test Conditions
25C, Vdd = 2.6 V
25C, Vdd = 2.6 V
© 2011 Kionix – All Rights Reserved
575-4177-1212131126
Page 7 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Package Dimensions and Orientation
3 x 3 x 0.9 mm LGA
All dimensions and tolerances conform to ASME Y14.5M-1994
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Page 8 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Orientation
+Y
Pin 1
+X
+Z
When device is accelerated in +X, +Y or +Z direction, the corresponding output will increase.
Static X/Y/Z Output Response versus Orientation to Earth’s surface (1g):
GSEL1=0, GSEL0=0 (± 2g)
Position
1
2
3
4
Diagram
Resolution (bits)
ddas((b(bits)
X (counts)
Y (counts)
Z (counts)
X-Polarity
Y-Polarity
Z-Polarity
12
8
0
0
1024 64
0
0
0
0
+
0
12
1024
0
0
+
0
0
8
64
0
0
12
0
-1024
0
8
0
-64
0
0
0
12
-1024
0
0
0
0
8
-64
0
0
5
Top
6
Bottom
Bottom
Top
12
8
0
0
0
0
1024 64
0
0
+
12
0
0
-1024
8
0
0
-64
0
0
-
(1g)
Earth’s Surface
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Page 9 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Static X/Y/Z Output Response versus Orientation to Earth’s surface (1g):
GSEL1=0, GSEL0=1 (± 4g)
Position
1
2
3
4
5
6
Top
Bottom
Diagram
Resolution (bits)
X (counts)
Y (counts)
Z (counts)
X-Polarity
Y-Polarity
Z-Polarity
Bottom
12
8
0
0
512 32
0
0
0
0
+
0
12
512
0
0
8
32
0
0
12
0
-512
0
+
0
0
8
0
-32
0
0
0
12
-512
0
0
8
-32
0
0
0
0
12
0
0
512
8
0
0
32
Top
12
0
0
-512
0
0
+
8
0
0
-32
0
0
-
(1g)
Earth’s Surface
Static X/Y/Z Output Response versus Orientation to Earth’s surface (1g):
GSEL1=1, GSEL0=0 (± 8g)
Position
1
2
3
4
5
Top
Diagram
Resolution (bits)
X (counts)
Y (counts)
Z (counts)
X-Polarity
Y-Polarity
Z-Polarity
6
Bottom
Top
12
8
0
0
256 16
0
0
0
0
+
0
12
256
0
0
8
16
0
0
+
0
0
12
0
-256
0
8
0
-16
0
0
0
(1g)
12
-256
0
0
0
0
8
-16
0
0
Bottom
12
8
0
0
0
0
256 16
0
0
+
12
0
0
-256
8
0
0
-16
0
0
-
Earth’s Surface
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Page 10 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
KXTI9 Digital Interface
The Kionix KXTI9 digital accelerometer has the ability to communicate on the I2C digital serial interface bus.
This flexibility allows for easy system integration by eliminating analog-to-digital converter requirements and by
providing direct communication with system micro-controllers. In doing so, all of the digital communication
pins have shared responsibilities.
The serial interface terms and descriptions as indicated in Table 6 below will be observed throughout this
document.
Term
Transmitter
Receiver
Master
Slave
Description
The device that transmits data to the bus.
The device that receives data from the bus.
The device that initiates a transfer, generates clock signals, and terminates a transfer.
The device addressed by the Master.
Table 6. Serial Interface Terminologies
I2C Serial Interface
As previously mentioned, the KXTI9 has the ability to communicate on an I2C bus. I2C is primarily used for
synchronous serial communication between a Master device and one or more Slave devices. The Master,
typically a micro controller, provides the serial clock signal and addresses Slave devices on the bus. The
KXTI9 always operates as a Slave device during standard Master-Slave I2C operation.
I2C is a two-wire serial interface that contains a Serial Clock (SCL) line and a Serial Data (SDA) line. SCL is a
serial clock that is provided by the Master, but can be held low by any Slave device, putting the Master into a
wait condition. SDA is a bi-directional line used to transmit and receive data to and from the interface. Data is
transmitted MSB (Most Significant Bit) first in 8-bit per byte format, and the number of bytes transmitted per
transfer is unlimited. The I2C bus is considered free when both lines are high.
I2C Operation
Transactions on the I2C bus begin after the Master transmits a start condition (S), which is defined as a highto-low transition on the data line while the SCL line is held high. The bus is considered busy after this
condition. The next byte of data transmitted after the start condition contains the Slave Address (SAD) in the
seven MSBs (Most Significant Bits), and the LSB (Least Significant Bit) tells whether the Master will be
receiving data ‘1’ from the Slave or transmitting data ‘0’ to the Slave. When a Slave Address is sent, each
device on the bus compares the seven MSBs with its internally stored address. If they match, the device
considers itself addressed by the Master. The Slave Address associated with the KXTI9 is 0001111.
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Page 11 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
It is mandatory that receiving devices acknowledge (ACK) each transaction. Therefore, the transmitter must
release the SDA line during this ACK pulse. The receiver then pulls the data line low so that it remains stable
low during the high period of the ACK clock pulse. A receiver that has been addressed, whether it is Master or
Slave, is obliged to generate an ACK after each byte of data has been received. To conclude a transaction,
the Master must transmit a stop condition (P) by transitioning the SDA line from low to high while SCL is high.
The I2C bus is now free.
Writing to a KXTI9 8-bit Register
Upon power up, the Master must write to the KXTI9’s control registers to set its operational mode. Therefore,
when writing to a control register on the I2C bus, as shown Sequence 1 on the following page, the following
protocol must be observed: After a start condition, SAD+W transmission, and the KXTI9 ACK has been
returned, an 8-bit Register Address (RA) command is transmitted by the Master. This command is telling the
KXTI9 to which 8-bit register the Master will be writing the data. Since this is I2C mode, the MSB of the RA
command should always be zero (0). The KXTI9 acknowledges the RA and the Master transmits the data to
be stored in the 8-bit register. The KXTI9 acknowledges that it has received the data and the Master transmits
a stop condition (P) to end the data transfer. The data sent to the KXTI9 is now stored in the appropriate
register. The KXTI9 automatically increments the received RA commands and, therefore, multiple bytes of
data can be written to sequential registers after each Slave ACK as shown in Sequence 2 on the following
page.
Reading from a KXTI9 8-bit Register
When reading data from a KXTI9 8-bit register on the I2C bus, as shown in Sequence 3 on the next page, the
following protocol must be observed: The Master first transmits a start condition (S) and the appropriate Slave
Address (SAD) with the LSB set at ‘0’ to write. The KXTI9 acknowledges and the Master transmits the 8-bit
RA of the register it wants to read. The KXTI9 again acknowledges, and the Master transmits a repeated start
condition (Sr). After the repeated start condition, the Master addresses the KXTI9 with a ‘1’ in the LSB
(SAD+R) to read from the previously selected register. The Slave then acknowledges and transmits the data
from the requested register. The Master does not acknowledge (NACK) it received the transmitted data, but
transmits a stop condition to end the data transfer. Note that the KXTI9 automatically increments through its
sequential registers, allowing data to be read from multiple registers following a single SAD+R command as
shown below in Sequence 4 on the following page.
If a receiver cannot transmit or receive another complete byte of data until it has performed some other
function, it can hold SCL low to force the transmitter into a wait state. Data transfer only continues when the
receiver is ready for another byte and releases SCL.
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Page 12 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Data Transfer Sequences
The following information clearly illustrates the variety of data transfers that can occur on the I 2C bus and how
the Master and Slave interact during these transfers. Table 7 defines the I2C terms used during the data
transfers.
Term
S
Sr
SAD
W
R
ACK
NACK
RA
Data
P
Definition
Start Condition
Repeated Start Condition
Slave Address
Write Bit
Read Bit
Acknowledge
Not Acknowledge
Register Address
Transmitted/Received Data
Stop Condition
Table 7. I2C Terms
Sequence 1. The Master is writing one byte to the Slave.
Master
Slave
S
SAD + W
RA
ACK
DATA
ACK
P
ACK
Sequence 2. The Master is writing multiple bytes to the Slave.
Master
Slave
S
SAD + W
RA
ACK
DATA
ACK
DATA
ACK
P
ACK
Sequence 3. The Master is receiving one byte of data from the Slave.
Master
Slave
S
SAD + W
RA
ACK
Sr
SAD + R
ACK
NACK
ACK
P
DATA
Sequence 4. The Master is receiving multiple bytes of data from the Slave.
Master
Slave
S
SAD + W
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RA
ACK
Sr
ACK
SAD + R
ACK
ACK
DATA
NACK
DATA
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Page 13 of 55
P
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
KXTI9 Embedded Registers
The KXTI9 has 44 embedded 8-bit registers that are accessible by the user. This section contains the
addresses for all embedded registers and also describes bit functions of each register. Table 8 below
provides a listing of the accessible 8-bit registers and their addresses.
Register Name
XOUT_HPF_L
XOUT_HPF_H
YOUT_HPF_L
YOUT_HPF_H
ZOUT_HPF_L
ZOUT_HPF_H
XOUT_L
XOUT_H
YOUT_L
YOUT_H
ZOUT_L
ZOUT_H
DCST_RESP
Not Used
Not Used
WHO_AM_I
TILT_POS_CUR
TILT_POS_PRE
Kionix Reserved
Kionix Reserved
Kionix Reserved
INT_SRC_REG1
INT_SRC_REG2
Not Used
STATUS_REG
Not Used
INT_REL
CTRL_REG1*
CTRL_REG2*
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Type
Read/Write
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R/W
R/W
I2C Address
Hex
Binary
0x00
0000 0000
0x01
0000 0001
0x02
0000 0010
0x03
0000 0011
0x04
0000 0100
0x05
0000 0101
0x06
0000 0110
0x07
0000 0111
0x08
0000 1000
0x09
0000 1001
0x0A
0000 1010
0x0B
0000 1011
0x0C
0000 1100
0x0D
0000 1101
0x0E
0000 1110
0x0F
0000 1111
0x10
0001 0000
0x11
0001 0001
0x12
0001 0010
0x13
0001 0011
0x14
0001 0100
0x15
0001 0101
0x16
0001 0110
0x17
0001 0111
0x18
0001 1000
0x19
0001 1001
0x1A
0001 1010
0x1B
0001 1011
0x1C
0001 1100
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Page 14 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
CTRL_REG3*
INT_CTRL_REG1*
INT_CTRL_REG2*
INT_CTRL_REG3*
DATA_CTRL_REG*
Not Used
TILT_TIMER*
WUF_TIMER*
Not Used
TDT_TIMER*
TDT_H_THRESH*
TDT_L_THRESH*
TDT_TAP_TIMER*
TDT_TOTAL_TIMER*
TDT_LATENCY_TIMER*
TDT_WINDOW_TIMER*
BUF_CTRL1*
BUF_CTRL2*
BUF_STATUS_REG1
BUF_STATUS_REG2
BUF_CLEAR
Reserved
SELF_TEST
Reserved
WUF_THRESH*
Reserved
TILT_ANGLE*
Reserved
HYST_SET*
BUF_READ
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
R
W
R/W
R/W
R/W
R/W
R
0x1D
0x1E
0x1F
0x20
0x21
0x22 – 0x27
0x28
0x29
0x2A
0x2B
0x2C
0x2D
0x2E
0x2F
0x30
0x31
0x32
0x33
0x34
0x35
0x36
0x37 – 0x39
0x3A
0x3B – 0x59
0x5A
0x5B
0x5C
0x5D – 0x5E
0x5F
0x7F
KXTI9-1001
Rev. 3
Dec-2012
0001 1101
0001 1110
0001 1111
0010 0000
0010 0001
0010 1000
0010 1001
0010 1010
0010 1011
0010 1100
0010 1101
0010 1110
0010 1111
0011 0000
0011 0001
0011 0010
0011 0011
0011 0100
0011 0101
0011 0110
0011 1010
0101 1010
0101 1011
0101 1100
0101 1111
0111 1111
* Note: When changing the contents of these registers, the PC1 bit in CTRL_REG1 must first
be set to “0”.
Table 8. KXTI9 Register Map
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
KXTI9 Register Descriptions
Accelerometer Outputs
These registers contain up to 12-bits of valid acceleration data for each axis depending on the setting
of the RES bit in CTRL_REG1, where the acceleration outputs are represented in 12-bit valid data
when RES = ‘1’ and 8-bit valid data when RES = ‘0’. The data is updated every user-defined ODR
period, is protected from overwrite during each read, and can be converted from digital counts to
acceleration (g) per Figure 1 below. The register acceleration output binary data is represented in N-bit
2’s complement format. For example, if N = 12 bits, then the Counts range is from -2048 to 2047, and if
N = 8 bits, then the Counts range is from -128 to 127.
12-bit
Register Data
(2’s complement)
0111 1111 1111
0111 1111 1110
…
0000 0000 0001
0000 0000 0000
1111 1111 1111
…
1000 0000 0001
1000 0000 0000
8-bit
Register Data
(2’s complement)
0111 1111
0111 1110
…
0000 0001
0000 0000
1111 1111
…
1000 0001
1000 0000
Equivalent
Counts in decimal
2047
2046
…
1
0
-1
…
-2047
-2048
Range = +/-2g
+1.999g
+1.998g
…
+0.001g
0.000g
-0.001g
…
-1.999g
-2.000g
Range = +/-4g
+3.998g
+3.996g
…
+0.002g
0.000g
-0.002g
…
-3.998g
-4.000g
Range = +/-8g
+7.996g
+7.992g
…
+0.004g
0.000g
-0.004g
…
-7.996g
-8.000g
Equivalent
Counts in decimal
127
126
…
1
0
-1
…
-127
-128
Range = +/-2g
+1.984g
+1.968g
…
+0.016g
0.000g
-0.016g
…
-1.984g
-2.000g
Range = +/-4g
+3.968g
+3.936g
…
+0.032g
0.000g
-0.032g
…
-3.968g
-4.000g
Range = +/-8g
+7.936g
+7.872g
…
+0.064g
0.000g
-0.064g
…
-7.936g
-8.000g
Figure 1. Acceleration (g) Calculation
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Note: The High Pass Filter outputs are only available if the Wake Up Function is enabled.
XOUT_HPF_L
X-axis high-pass filtered accelerometer output least significant byte
R
XOUTD3
Bit7
R
XOUTD2
Bit6
R
XOUTD1
Bit5
R
XOUTD0
Bit4
R
X
Bit3
R
X
Bit2
R
R
X
X
Bit1
Bit0
2
I C Address: 0x00h
XOUT_HPF_H
X-axis high-pass filtered accelerometer output most significant byte
R
R
R
XOUTD11 XOUTD10 XOUTD9
Bit7
Bit6
Bit5
R
XOUTD8
Bit4
R
XOUTD7
Bit3
R
XOUTD6
Bit2
R
R
XOUTD5 XOUTD4
Bit1
Bit0
2
I C Address: 0x01h
YOUT_HPF_L
Y-axis high-pass filtered accelerometer output least significant byte
R
YOUTD3
Bit7
R
YOUTD2
Bit6
R
YOUTD1
Bit5
R
YOUTD0
Bit4
R
X
Bit3
R
X
Bit2
R
R
X
X
Bit1
Bit0
2
I C Address: 0x02h
YOUT_HPF_H
Y-axis high-pass filtered accelerometer output most significant byte
R
R
R
YOUTD11 YOUTD10 YOUTD9
Bit7
Bit6
Bit5
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R
YOUTD8
Bit4
R
YOUTD7
Bit3
R
R
R
YOUTD6 YOUTD5 YOUTD4
Bit2
Bit1
Bit0
2
I C Address: 0x03h
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
ZOUT_HPF_L
Z-axis high-pass filtered accelerometer output least significant byte
R
ZOUTD3
Bit7
R
ZOUTD2
Bit6
R
ZOUTD1
Bit5
R
ZOUTD0
Bit4
R
X
Bit3
R
X
Bit2
R
R
X
X
Bit1
Bit0
2
I C Address: 0x04h
ZOUT_HPF_H
Z-axis high-pass filtered accelerometer output most significant byte
R
R
R
ZOUTD11 ZOUTD10 ZOUTD9
Bit7
Bit6
Bit5
R
ZOUTD8
Bit4
R
ZOUTD7
Bit3
R
R
R
ZOUTD6 ZOUTD5 ZOUTD4
Bit2
Bit1
Bit0
2
I C Address: 0x05h
XOUT_L
X-axis accelerometer output least significant byte
R
XOUTD3
Bit7
R
XOUTD2
Bit6
R
XOUTD1
Bit5
R
XOUTD0
Bit4
R
X
Bit3
R
X
Bit2
R
R
X
X
Bit1
Bit0
2
I C Address: 0x06h
XOUT_H
X-axis accelerometer output most significant byte
R
R
R
XOUTD11 XOUTD10 XOUTD9
Bit7
Bit6
Bit5
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R
XOUTD8
Bit4
R
XOUTD7
Bit3
R
R
R
XOUTD6 XOUTD5 XOUTD4
Bit2
Bit1
Bit0
2
I C Address: 0x07h
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
YOUT_L
Y-axis accelerometer output least significant byte
R
YOUTD3
Bit7
R
YOUTD2
Bit6
R
YOUTD1
Bit5
R
YOUTD0
Bit4
R
X
Bit3
R
X
Bit2
R
R
X
X
Bit1
Bit0
2
I C Address: 0x08h
YOUT_H
Y-axis accelerometer output most significant byte
R
R
R
YOUTD11 YOUTD10 YOUTD9
Bit7
Bit6
Bit5
R
YOUTD8
Bit4
R
YOUTD7
Bit3
R
R
R
YOUTD6 YOUTD5 YOUTD4
Bit2
Bit1
Bit0
2
I C Address: 0x09h
ZOUT_L
Z-axis accelerometer output least significant byte
R
ZOUTD3
Bit7
R
ZOUTD2
Bit6
R
ZOUTD1
Bit5
R
ZOUTD0
Bit4
R
X
Bit3
R
X
Bit2
R
R
X
X
Bit1
Bit0
2
I C Address: 0x0Ah
ZOUT_H
Z-axis accelerometer output most significant byte
R
R
R
ZOUTD11 ZOUTD10 ZOUTD9
Bit7
Bit6
Bit5
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R
ZOUTD8
Bit4
R
ZOUTD7
Bit3
R
R
R
ZOUTD6 ZOUTD5 ZOUTD4
Bit2
Bit1
Bit0
2
I C Address: 0x0Bh
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
DCST_RESP
This register can be used to verify proper integrated circuit functionality. It always has a byte value of
0x55h unless the DCST bit in CTRL_REG3 is set. At that point this value is set to 0xAAh. The byte
value is returned to 0x55h after reading this register.
R
DCSTR7
Bit7
R
DCSTR6
Bit6
R
DCSTR5
Bit5
R
DCSTR4
Bit4
R
DCSTR3
Bit3
R
DCSTR2
Bit2
R
R
DCSTR1 DCSTR0
Bit1
Bit0
2
I C Address: 0x0Ch
Reset Value
01010101
WHO_AM_I
This register can be used for supplier recognition, as it can be factory written to a known byte value.
The default value is 0x04h.
R
WIA7
Bit7
R
WIA6
Bit6
R
WIA5
Bit5
R
WIA4
Bit4
R
WIA3
Bit3
R
WIA2
Bit2
R
R
WIA1
WIA0
Bit1
Bit0
2
I C Address: 0x0Fh
Reset Value
00000100
Tilt Position Registers
These two registers report previous and current tilt position data that is updated at the user-defined
ODR frequency and is protected during register read. Table 9 describes the reported position for each
bit value.
TILT_POS_CUR
Current tilt position register
R
0
Bit7
R
0
Bit6
R
LE
Bit5
R
RI
Bit4
R
DO
Bit3
R
UP
Bit2
R
R
FD
FU
Bit1
Bit0
2
I C Address: 0x10h
Reset Value
00100000
R
DO
Bit3
R
UP
Bit2
R
R
FD
FU
Bit1
Bit0
2
I C Address: 0x11h
Reset Value
00100000
TILT_POS_PRE
Previous tilt position register
R
0
Bit7
R
0
Bit6
R
LE
Bit5
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R
RI
Bit4
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
Bit
LE
RI
DO
UP
FD
FU
KXTI9-1001
Rev. 3
Dec-2012
Description
Left State (X-)
Right State (X+)
Down State (Y-)
Up State (Y+)
Face-Down State (Z-)
Face-Up State (Z+)
Table 9. KXTI9 Tilt Position
Interrupt Source Registers
These two registers report function state changes. This data is updated when a new state change or
event occurs and each application’s result is latched until the interrupt release register is read. The
motion interrupt bit WUFS can be configured to report data in an unlatched manner via the interrupt
control registers.
INT_SRC_REG1
This register reports which axis and direction detected a single or double tap event, per Table
10.
R
0
Bit7
R
0
Bit6
R
TLE
Bit5
R
TRI
Bit4
R
TDO
Bit3
Bit
TLE
TRI
TDO
TUP
TFD
TFU
R
TUP
Bit2
R
R
TFD
TFU
Bit1
Bit0
2
I C Address: 0x15h
Description
X Negative (X-) Reported
X Positive (X+) Reported
Y Negative (Y-) Reported
Y Positive (Y+) Reported
Z Negative (Z-) Reported
Z Positive (Z+) Reported
Table 10. KXTI9 Directional TapTM Reporting
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
INT_SRC_REG2
This register reports which function caused an interrupt. Reading from the interrupt release
register will clear the entire contents of this register.
R
0
Bit7
R
0
Bit6
R
WMI
Bit5
R
DRDY
Bit4
R
TDTS1
Bit3
R
TDTS0
Bit2
R
R
WUFS
TPS
Bit1
Bit0
2
I C Address: 0x16h
DRDY indicates that new acceleration data is available. This bit is cleared when
acceleration data is read or the interrupt release register is read.
DRDY = 0 – new acceleration data not available
DRDY = 1 – new acceleration data available
TDTS1, TDTS0 indicates whether a single or double-tap event was detected per Table
11.
TDTS1 TDTS0
Event
0
0
No Tap
0
1
Single Tap
1
0
Double Tap
1
1
DNE
Table 11. Directional TapTM Event Description
WUFS - Wake up, This bit is cleared when acceleration data is read or the interrupt
release register is read.
0 = No motion
1 = Motion has activated the interrupt
TPS reflects the status of the tilt position function.
TPS = 0 – tilt position state has not changed
TPS = 1 – tilt position state has changed
WMI indicates that the buffer’s sample threshold has been reached when in FIFO, FILO,
or Stream mode. Not used in Trigger mode.
WMI = 0 – sample threshold has not been reached
WMI = 1 – sample threshold has been reached
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
STATUS_REG
This register reports the status of the interrupt.
R
0
Bit7
R
0
Bit6
R
0
Bit5
R
INT
Bit4
R
0
Bit3
R
0
Bit2
R
R
0
0
Bit1
Bit0
2
I C Address: 0x18h
INT reports the combined interrupt information of all enabled functions. This bit is released to
0 when the interrupt source latch register (1Ah) is read.
INT = 0 – no interrupt event
INT = 1 – interrupt event has occurred
INT_REL
Latched interrupt source information (INT_SRC_REG1 and INT_SRC_REG2), the status register, and
the physical interrupt pin (7) are cleared when reading this register.
R
X
Bit7
R
X
Bit6
R
X
Bit5
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R
X
Bit4
R
X
Bit3
R
X
Bit2
R
R
X
X
Bit1
Bit0
2
I C Address: 0x1Ah
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
CTRL_REG1
Read/write control register that controls the main feature set.
R/W
PC1
Bit7
R/W
RES
Bit6
R/W
DRDYE
Bit5
R/W
GSEL1
Bit4
R/W
GSEL0
Bit3
R/W
TDTE
Bit2
R/W
R/W
WUFE
TPE
Bit1
Bit0
2
I C Address: 0x1Bh
Reset Value
00000000
PC1 controls the operating mode of the KXTI9.
PC1 = 0 - stand-by mode
PC1 = 1 – operating mode
RES determines the performance mode of the KXTI9. Note that to change the value of this
bit, the PC1 bit must first be set to “0”.
RES = 0 – low current, 8-bit valid
RES = 1- high current, 12-bit valid
DRDYE enables the reporting of the availability of new acceleration data as an interrupt. Note
that to change the value of this bit, the PC1 bit must first be set to “0”.
DRDYE = 0 – availability of new acceleration data not available
DRDYE = 1- availability of new acceleration data available
GSEL1, GSEL0 selects the acceleration range of the accelerometer outputs per Table 12.
Note that to change the value of this bit, the PC1 bit must first be set to “0”.
GSEL1 GSEL0
0
0
0
1
1
0
1
1
Range
+/-2g
+/-4g
+/-8g
NA
Table 12. Selected Acceleration Range
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
TDTE enables the Directional TapTM function that will detect single and double tap events.
Note that to change the value of this bit, the PC1 bit must first be set to “0”.
TDTE = 0 – disable
TDTE = 1- enable
WUFE enables the Wake Up (motion detect) function that will detect a general motion event.
Note that to change the value of this bit, the PC1 bit must first be set to “0”.
WUFE = 0 – disable
WUFE = 1- enable
TPE enables the Tilt Position function that will detect changes in device orientation. Note that
to change the value of this bit, the PC1 bit must first be set to “0”.
TPE = 0 – disable
TPE = 1- enable
CTRL_REG2
Read/write control register that primarily controls tilt position state enabling. Per Table 13, if a state’s
bit is set to one (1), a transition into the corresponding orientation state will generate an interrupt. If it is
set to zero (0), a transition into the corresponding orientation state will not generate an interrupt. Note
that to properly change the value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”.
R/W
OTDTH
Bit7
R/W
0
Bit6
R/W
LEM
Bit5
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R/W
RIM
Bit4
R/W
DOM
Bit3
R/W
UPM
Bit2
R/W
R/W
FDM
FUM
Bit1
Bit0
2
I C Address: 0x1Ch
Reset Value
00111111
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
OTDTH determines the range of the Directional TapTM Output Data Rate (ODR). See Table
15 for additional clarification.
OTDTH = 0 – slower range of Directional TapTM ODR’s are available.
OTDTH = 1 – faster range of Directional TapTM ODR’s are available.
Bit
LEM
RIM
DOM
UPM
FDM
FUM
Description
Left State
Right State
Down State
Up State
Face-Down State
Face-Up State
Table 13. Tilt Position State Enabling
CTRL_REG3
Read/write control register that provides more feature set control. Note that to properly change the
value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”.
R/W
SRST
Bit7
R/W
OTPA
Bit6
R/W
OTPB
Bit5
R/W
DCST
Bit4
R/W
OTDTA
Bit3
R/W
OTDTB
Bit2
R/W
R/W
OWUFA OWUFB
Bit1
Bit0
2
I C Address: 0x1Dh
Reset Value
01001101
SRST initiates software reset, which performs the RAM reboot routine. This bit will remain 1
until the RAM reboot routine is finished.
SRST = 0 – no action
SRST = 1 – start RAM reboot routine
Note for I2C Communication: Setting SRST = 1 will NOT result in an ACK, since the part
immediately enters the RAM reboot routine. NACK may be used to confirm this
command.
OTPA, OTPB sets the output data rate for the Tilt Position function per Table 14. The default
Tilt Position ODR is 12.5Hz.
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
OTPA
0
0
1
1
OTPB
0
1
0
1
KXTI9-1001
Rev. 3
Dec-2012
Output Data Rate
1.6Hz
6.3Hz
12.5Hz
50Hz
Table 14. Tilt Position Function Output Data Rate
DCST initiates the digital communication self-test function.
DCST = 0 – no action
DCST = 1 – sets ST_RESP register to 0xAAh and when ST_RESP is read, sets this
bit to 0 and sets ST_RESP to 0x55h
OTDTA, OTDTB sets the output data rate for the Directional TapTM function per Table 15.
The default Directional TapTM ODR is 400Hz.
OTDTH OTDTA OTDTB Output Data Rate
0
0
0
50Hz
0
0
1
100Hz
0
1
0
200Hz
0
1
1
400Hz
1
0
0
12.5Hz
1
0
1
25Hz
1
1
0
800Hz
1
1
1
1600Hz
Table 15. Directional TapTM Function Output Data Rate
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
OWUFA, OWUFB sets the output data rate for the general motion detection function and the
high-pass filtered outputs per Table 16. The default Motion Wake Up ODR is 50Hz.
OWUFA OWUFB Output Data Rate
0
0
25Hz
0
1
50Hz
1
0
100Hz
1
1
200Hz
Table 16. Motion Wake Up Function Output Data Rate
INT_CTRL_REG1
This register controls the settings for the physical interrupt pin (7). Note that to properly change the
value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”.
R/W
0
Bit7
R/W
0
Bit6
R/W
IEN
Bit5
R/W
IEA
Bit4
R/W
IEL
Bit3
R/W
IEU
Bit2
R/W
R/W
0
0
Bit1
Bit0
2
I C Address: 0x1Eh
Reset Value
00010000
IEN enables/disables the physical interrupt pin (7)
IEN = 0 – physical interrupt pin (7) is disabled
IEN = 1 – physical interrupt pin (7) is enabled
IEA sets the polarity of the physical interrupt pin (7)
IEA = 0 – polarity of the physical interrupt pin (7) is active low
IEA = 1 – polarity of the physical interrupt pin (7) is active high
IEL sets the response of the physical interrupt pin (7)
IEL = 0 – the physical interrupt pin (7) latches until it is cleared by reading INT_REL
IEL = 1 – the physical interrupt pin (7) will transmit one pulse with a period of
approximately 0.03 - 0.05ms
IEU sets an alternate unlatched response for the physical interrupt pin (7) when the motion
interrupt feature (WUF) only is enabled.
IEU = 0 – the physical interrupt pin (7) latches or pulses per the IEL bit until it is cleared
by reading INT_REL
IEU = 1 – the physical interrupt pin (7) will follow an unlatched response if the motion
interrupt feature is enabled
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
INT_CTRL_REG2
This register controls motion detection axis enabling. Per Table 17, if an axis’ bit is set to one (1), a
motion on that axis will generate an interrupt. If it is set to zero (0), a motion on that axis will not
generate an interrupt. Note that to properly change the value of this register, the PC1 bit in
CTRL_REG1 must first be set to “0”.
R/W
XBW
Bit7
R/W
YBW
Bit6
R/W
ZBW
Bit5
R/W
0
Bit4
R/W
0
Bit3
R/W
0
Bit2
R/W
0
Bit1
R/W
0
Bit0
Reset Value
11100000
2
I C Address: 0x1Fh
Bit
XBW
YBW
ZBW
Description
X-Axis Motion
Y-Axis Motion
Z-Axis Motion
Table 17. Motion Detection Axis Enabling
INT_CTRL_REG3
This register controls the tap detection direction axis enabling. Per Table 18, if a direction’s bit is set
to one (1), a single or double tap in that direction will generate an interrupt. If it is set to zero (0), a
single or double tap in that direction will not generate an interrupt. Note that to properly change the
value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”.
R/W
0
Bit7
R/W
TMEN
Bit6
R/W
TLEM
Bit5
R/W
TRIM
Bit4
R/W
TDOM
Bit3
Bit
TLEM
TRIM
TDOM
TUPM
TFDM
TFUM
R/W
TUPM
Bit2
R/W
R/W
TFDM
TFUM
Bit1
Bit0
2
I C Address: 0x20h
Reset Value
00111111
Description
X Negative (X-)
X Positive (X+)
Y Negative (Y-)
Y Positive (Y+)
Z Negative (Z-)
Z Positive (Z+)
Table 18. Directional TapTM Axis Mask
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
TMEN enables/disables alternate tap masking scheme
TMEN = 0 – alternate tap masking scheme disabled
TMEN = 1 – alternate tap masking scheme enabled
DATA_CTRL_REG
Read/write control register that configures the acceleration outputs. Note that to properly change the
value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”.
R/W
0
Bit7
R/W
0
Bit6
R/W
HPFROA
Bit5
R/W
HPROB
Bit4
R/W
0
Bit3
R/W
OSAA
Bit2
R/W
R/W
OSAB
OSAC
Bit1
Bit0
2
I C Address: 0x21h
Reset Value
00000010
HPFROA, HPFROB sets the roll-off frequency for the first-order high-pass filter in conjunction
with the output data rate (OWUFA, OWUFB) that is chosen for the HPF acceleration outputs
that are used in the Motion Wake Up (WUF) application per Table 19. Note that this roll-off
frequency is also applied to the X, Y and Z high-pass filtered outputs.
High-Pass Filter Configuration
HPFROA HPFROB Beta HPF Roll-Off (Hz)
0
0
7/8
ODR / 50
0
1
15/16
ODR / 100
1
0
31/32
ODR / 200
1
1
63/64
ODR / 400
Table 19. High-Pass Filter Roll-Off Frequency
OSAA, OSAB, OSAC sets the output data rate (ODR) for the low-pass filtered acceleration
outputs per Table 20.
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
OSAA
0
0
0
0
1
1
1
1
OSAB
0
0
1
1
0
0
1
1
OSAC
0
1
0
1
0
1
0
1
Output Data Rate
12.5Hz
25Hz
50Hz
100Hz
200Hz
400Hz
800Hz
Does Not Exist
KXTI9-1001
Rev. 3
Dec-2012
LPF Roll-Off
6.25Hz
12.5Hz
25Hz
50Hz
100Hz
200Hz
400Hz
Does Not Exist
Table 20. LPF Acceleration Output Data Rate (ODR)
TILT_TIMER
This register is the initial count register for the tilt position state timer (0 to 255 counts). Every count is
calculated as 1/ODR delay period, where the Tilt Position ODR is user-defined per Table 14. A new
state must be valid as many measurement periods before the change is accepted. Note that to properly
change the value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”.
R/W
TSC7
Bit7
R/W
TSC6
Bit6
R/W
TSC5
Bit5
R/W
TSC4
Bit4
R/W
TSC3
Bit3
R/W
TSC2
Bit2
R/W
R/W
TSC1
TSC0
Bit1
Bit0
2
I C Address: 0x28h
Reset Value
00000000
WUF_TIMER
This register is the initial count register for the motion detection timer (0 to 255 counts). Every count is
calculated as 1/ODR delay period, where the Motion Wake Up ODR is user-defined per Table 16. A
new state must be valid as many measurement periods before the change is accepted. Note that to
properly change the value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”.
R/W
WUFC7
Bit7
R/W
WUFC6
Bit6
R/W
WUFC5
Bit5
R/W
WUFC4
Bit4
R/W
WUFC3
Bit3
R/W
WUFC2
Bit2
R/W
WUFC1
Bit1
R/W
WUFC0
Bit0
Reset Value
00000000
2
I C Address: 0x29h
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
TDT_TIMER
This register contains counter information for the detection of a double tap event. When the Directional
TapTM ODR is 400Hz or less, every count is calculated as 1/ODR delay period. When the Directional
TapTM ODR is 800Hz, every count is calculated as 2/ODR delay period. When the Directional TapTM
ODR is 1600Hz, every count is calculated as 4/ODR delay period. The Directional TapTM ODR is userdefined per Table 15. TDT_TIMER represents the minimum time separation between the first tap and
the second tap in a double tap event. The Kionix recommended default value is 0.3 seconds (0x78h).
Note that to properly change the value of this register, the PC1 bit in CTRL_REG1 must first be set to
“0”.
R/W
TDTC7
Bit7
R/W
TDTC6
Bit6
R/W
TDTC5
Bit5
R/W
TDTC4
Bit4
R/W
TDTC3
Bit3
R/W
TDTC2
Bit2
R/W
R/W
TDTC1
TDTC0
Bit1
Bit0
2
I C Address: 0x2Bh
Reset Value
01111000
TDT_H_THRESH
This register represents the 8-bit jerk high threshold to determine if a tap is detected. Though this is an
8-bit register, the KXTI9 internally multiplies the register value by two in order to set the high threshold.
This multiplication results in a range of 0d to 510d with a resolution of two counts. The Performance
Index (PI) is the jerk signal that is expected to be less than this threshold, but greater than the
TDT_L_THRESH threshold during single and double tap events. Note that to properly change the
value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”. The Kionix recommended
default value is 203 (0xCBh) and the Performance Index is calculated as:
X’ = X(current) – X(previous)
Y’ = Y(current) – Y(previous)
Z’ = Z(current) – Z(previous)
PI = |X’| + |Y’| + |Z’|
Equation 1. Performance Index
R/W
TTH7
Bit7
R/W
TTH6
Bit6
R/W
TTH5
Bit5
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R/W
TTH4
Bit4
R/W
TTH3
Bit3
R/W
TTH2
Bit2
R/W
R/W
TTH1
TTH0
Bit1
Bit0
2
I C Address: 0x2Ch
Reset Value
11001011
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Page 32 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
TDT_L_THRESH
This register represents the 8-bit (0d– 255d) jerk low threshold to determine if a tap is detected. The
Performance Index (PI) is the jerk signal that is expected to be greater than this threshold and less
than the TDT_H_THRESH threshold during single and double tap events. This register also contains
the LSB of the TDT_H_THRESH threshold. The Kionix recommended default value is 26 (0x1Ah).
Note that to properly change the value of this register, the PC1 bit in CTRL_REG1 must first be set to
“0”.
R/W
TTH7
Bit7
R/W
TTL6
Bit6
R/W
TTL5
Bit5
R/W
TTL4
Bit4
R/W
TTL3
Bit3
R/W
TTL2
Bit2
R/W
R/W
TTL1
TTL0
Bit1
Bit0
2
I C Address: 0x2Dh
Reset Value
00011010
TDT_TAP_TIMER
This register contains counter information for the detection of any tap event. When the Directional
TapTM ODR is 400Hz or less, every count is calculated as 1/ODR delay period. When the Directional
TapTM ODR is 800Hz, every count is calculated as 2/ODR delay period. When the Directional TapTM
ODR is 1600Hz, every count is calculated as 4/ODR delay period. The Directional TapTM ODR is userdefined per Table 15. In order to ensure that only tap events are detected, these time limits are used.
A tap event must be above the performance index threshold (TDT_THRESH) for at least the low limit
(FTDL0 – FTDL2) and no more than the high limit (FTDH0 – FTDH4). The Kionix recommended
default value for the high limit is 0.05 seconds and for the low limit is 0.005 seconds (0xA2h). Note
that to properly change the value of this register, the PC1 bit in CTRL_REG1 must first be set to “0”.
R/W
FTDH4
Bit7
R/W
FTDH3
Bit6
R/W
FTDH2
Bit5
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R/W
FTDH1
Bit4
R/W
FTDH0
Bit3
R/W
FTDL2
Bit2
R/W
R/W
FTDL1
FTDL0
Bit1
Bit0
2
I C Address: 0x2Eh
Reset Value
10100010
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Page 33 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
TDT_TOTAL_TIMER
This register contains counter information for the detection of a double tap event. When the Directional
TapTM ODR is 400Hz or less, every count is calculated as 1/ODR delay period. When the Directional
TapTM ODR is 800Hz, every count is calculated as 2/ODR delay period. When the Directional TapTM
ODR is 1600Hz, every count is calculated as 4/ODR delay period. The Directional TapTM ODR is userdefined per Table 15. In order to ensure that only tap events are detected, this time limit is used. This
register sets the total amount of time that the two taps in a double tap event can be above the PI
threshold (TDT_L_THRESH). The Kionix recommended default value for TDT_TOTAL_TIMER is 0.09
seconds (0x24h). Note that to properly change the value of this register, the PC1 bit in CTRL_REG1
must first be set to “0”.
R/W
STD7
Bit7
R/W
STD6
Bit6
R/W
STD5
Bit5
R/W
STD4
Bit4
R/W
STD3
Bit3
R/W
STD2
Bit2
R/W
R/W
STD1
STD0
Bit1
Bit0
2
I C Address: 0x2Fh
Reset Value
00100100
TDT_LATENCY_TIMER
This register contains counter information for the detection of a tap event. When the Directional Tap TM
ODR is 400Hz or less, every count is calculated as 1/ODR delay period. When the Directional Tap TM
ODR is 800Hz, every count is calculated as 2/ODR delay period. When the Directional TapTM ODR is
1600Hz, every count is calculated as 4/ODR delay period. The Directional TapTM ODR is user-defined
per Table 15. In order to ensure that only tap events are detected, this time limit is used. This register
sets the total amount of time that the tap algorithm will count samples that are above the PI threshold
(TDT_L_THRESH) during a potential tap event. It is used during both single and double tap events.
However, reporting of single taps on the physical interrupt pin (7) will occur at the end of the
TDT_WINDOW_TIMER. The Kionix recommended default value for TDT_LATENCY_TIMER is 0.1
seconds (0x28h). Note that to properly change the value of this register, the PC1 bit in CTRL_REG1
must first be set to “0”.
R/W
TLT7
Bit7
R/W
TLT6
Bit6
R/W
TLT5
Bit5
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R/W
TLT4
Bit4
R/W
TLT3
Bit3
R/W
TLT2
Bit2
R/W
R/W
TLT1
TLT0
Bit1
Bit0
2
I C Address: 0x30h
Reset Value
00101000
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Page 34 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
TDT_WINDOW_TIMER
This register contains counter information for the detection of single and double taps. When the
Directional TapTM ODR is 400Hz or less, every count is calculated as 1/ODR delay period. When the
Directional TapTM ODR is 800Hz, every count is calculated as 2/ODR delay period. When the
Directional TapTM ODR is 1600Hz, every count is calculated as 4/ODR delay period. The Directional
TapTM ODR is user-defined per Table 15. It defines the time window for the entire tap event, single or
double, to occur. Reporting of single taps on the physical interrupt pin (7) will occur at the end of this
tap window. The Kionix recommended default value for TDT_WINDOW_TIMER is 0.4 seconds
(0xA0h). Note that to properly change the value of this register, the PC1 bit in CTRL_REG1 must first
be set to “0”.
R/W
TWS7
Bit7
R/W
TWS6
Bit6
R/W
TWS5
Bit5
R/W
TWS4
Bit4
R/W
TWS3
Bit3
R/W
TWS2
Bit2
R/W
R/W
TWS1
TWS0
Bit1
Bit0
2
I C Address: 0x31h
Reset Value
10100000
BUF_CTRL1
Read/write control register that controls the buffer sample threshold.
R/W
Bit7
R/W
R/W
R/W
R/W
R/W
R/W
R/W
SMP_TH6 SMP_TH5 SMP_TH4 SMP_TH3 SMP_TH2 SMP_TH1 SMP_TH0
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
2
I C Address: 0x32h
Reset Value
00000000
SMP_TH[6:0] Sample Threshold; determines the number of samples that will trigger a
watermark interrupt or will be saved prior to a trigger event. When BUF_RES=1, the
maximum number of samples is 41; when BUF_RES=0, the maximum number of
samples is 84.
Buffer Model
Sample Function
Bypass
None
FIFO
Stream
Trigger
FILO
Specifies how many buffer sample are needed
to trigger a watermark interrupt.
Specifies how many buffer samples are needed
to trigger a watermark interrupt.
Specifies how many buffer samples before the
trigger event are retained in the buffer.
Specifies how many buffer samples are needed
to trigger a watermark interrupt.
Table 21. Sample Threshold Operation by Buffer Mode
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
BUF_CTRL2
Read/write control register that controls sample buffer operation.
R/W
BUFE
Bit7
R/W
BUF_RES
Bit6
R/W
0
Bit5
R/W
0
Bit4
R/W
0
Bit3
R/W
0
Bit2
R/W
R/W
BUF_M1 BUF_M0
Bit1
Bit0
2
I C Address: 0x33h
Reset Value
00000000
BUFE controls activation of the sample buffer.
BUFE = 0 – sample buffer inactive
BUFE = 1 – sample buffer active
BUF_RES determines the resolution of the acceleration data samples collected by the sample
buffer.
BUF_RES = 0 – 8-bit samples are accumulated in the buffer
BUF_RES = 1 – 12-bit samples are accumulated in the buffer
BUF_M1, BUF_M0 selects the operating mode of the sample buffer per Table 22.
BUF_M1
BUF_M0
Mode
0
0
FIFO
0
1
Stream
1
0
Trigger
1
1
FILO
Description
The buffer collects 84 sets of 8-bit low resolution values or 41
sets of 12bit high resolution values and then stops collecting
data, collecting new data only when the buffer is not full.
The buffer holds the last 84 sets of 8-bit low resolution values
or 41 sets of 12bit high resolution values. Once the buffer is
full, the oldest data is discarded to make room for newer
data.
When a trigger event occurs, the buffer holds the last data
set of SMP[6:0] samples before the trigger event and then
continues to collect data until full. New data is collected only
when the buffer is not full.
The buffer holds the last 84 sets of 8-bit low resolution values
or 41 sets of 12bit high resolution values. Once the buffer is
full, the oldest data is discarded to make room for newer
data. Reading from the buffer in this mode will return the
most recent data first.
Table 22. Selected Buffer Mode
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
BUF_STATUS_REG1
This register reports the status of the sample buffer.
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
SMP_LEV7 SMP_LEV6 SMP_LEV5 SMP_LEV4 SMP_LEV3 SMP_LEV2 SMP_LEV1 SMP_LEV0
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
2
I C Address: 0x34h
SMP_LEV[7:0] Sample Level; reports the number of data bytes that have been stored in the
sample buffer. When BUF_RES=1, this count will increase by 6 for each 3-axis
sample in the buffer; when BUF_RES=0, the count will increase by 3 for each 3-axis
sample. If this register reads 0, no data has been stored in the buffer.
BUF_STATUS_REG2
This register reports the status of the sample buffer trigger function.
R/W
BUF_TRIG
Bit7
R/W
0
Bit6
R/W
0
Bit5
R/W
0
Bit4
R/W
0
Bit3
R/W
0
Bit2
R/W
R/W
0
0
Bit1
Bit0
2
I C Address: 0x35h
BUF_TRIG reports the status of the buffer’s trigger function if this mode has been selected.
When using trigger mode, a buffer read should only be performed after a trigger event.
BUF_CLEAR
Latched buffer status information and the entire sample buffer are cleared when any data is written to
this register.
R/W
X
Bit7
R/W
X
Bit6
R/W
X
Bit5
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R/W
X
Bit4
R/W
X
Bit3
R/W
X
Bit2
R/W
R/W
X
X
Bit1
Bit0
2
I C Address: 0x36h
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Page 37 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
SELF_TEST
When 0xCA is written to this register, the MEMS self-test function is enabled. Electrostatic-actuation of
the accelerometer, results in a DC shift of the X, Y and Z axis outputs. Writing 0x00 to this register will
return the accelerometer to normal operation.
R/W
1
Bit7
R/W
1
Bit6
R/W
0
Bit5
R/W
0
Bit4
R/W
1
Bit3
R/W
0
Bit2
R/W
R/W
1
0
Bit1
Bit0
2
I C Address: 0x3Ah
Reset Value
00000000
WUF_THRESH
This register sets the acceleration threshold, WUF Threshold that is used to detect a general motion
input. WUF_THRESH scales with GSEL1-GSEL0 in CTRL_REG1, and the KXTI9 will ship from the
factory with this value set to correspond to a change in acceleration of 0.5g when configured to
+/8g. Note that to properly change the value of this register, the PC1 bit in CTRL_REG1 must first be set
to “0”.
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
WUFTH7 WUFTH6 WUFTH5 WUFTH4 WUFTH3 WUFTH2 WUFTH1 WUFTH0
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0
2
I C Address: 0x5Ah
Reset Value
00001000
TILT_ANGLE
This register sets the tilt angle that is used to detect the transition from Face-up/Face-down states to
Screen Rotation states. The KXTI9 ships from the factory with tilt angle set to a low threshold of 26°
from horizontal. A different default tilt angle can be requested from the factory. Note that the minimum
suggested tilt angle is 10°. Note that to properly change the value of this register, the PC1 bit in
CTRL_REG1 must first be set to “0”.
R/W
TA7
Bit7
R/W
TA6
Bit6
R/W
TA5
Bit5
R/W
TA4
Bit4
R/W
TA3
Bit3
R/W
TA2
Bit2
R/W
TA1
Bit1
R/W
TA0
Bit0
Reset Value
00001100
2
I C Address: 0x5Ch
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
HYST_SET
This register sets the Hysteresis that is placed in between the Screen Rotation states. The KXTI9
ships from the factory with HYST_SET set to +/-15° of hysteresis. A different default hysteresis can be
requested from the factory. Note that when writing a new value to this register the current values of
RES0, RES1 and RES2 must be preserved. These values are set at the factory and must not change.
Note that to properly change the value of this register, the PC1 bit in CTRL_REG1 must first be set to
“0”.
R/W
RES2
Bit7
R/W
RES1
Bit6
R/W
RES0
Bit5
R/W
HYST4
Bit4
R/W
HYST3
Bit3
R/W
HYST2
Bit2
R/W
HYST1
Bit1
R/W
HYST0
Bit0
Reset Value
---10100
2
I C Address: 0x5Fh
BUF_READ
Data in the buffer can be read according to the BUF_RES and BUF_M settings in BUF_CTRL2 by
executing this command. More samples can be retrieved by continuing to toggle SCL after the read
command is executed. Data should only be read by set (6 bytes for high-resolution samples and 3
bytes for low-resolution samples) and by using auto-increment. Additional samples cannot be written
to the buffer while data is being read from the buffer using auto-increment mode. Output data is in 2’s
Complement format.
R/W
X
Bit7
R/W
X
Bit6
R/W
X
Bit5
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R/W
X
Bit4
R/W
X
Bit3
R/W
X
Bit2
R/W
R/W
X
X
Bit1
Bit0
2
I C Address: 0x7Fh
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Page 39 of 55
PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
KXTI9 Embedded Applications
Orientation Detection Feature
The orientation detection feature of the KXTI9 will report changes in face up, face down, +/- vertical and +/horizontal orientation. This intelligent embedded algorithm considers very important factors that provide
accurate orientation detection from low cost tri-axis accelerometers. Factors such as: hysteresis, device
orientation angle and delay time are described below as these techniques are utilized inside the KXTI9.
Hysteresis
A 45° tilt angle threshold seems like a good choice because it is halfway between 0° and 90°. However,
a problem arises when the user holds the device near 45°. Slight vibrations, noise and inherent sensor
error will cause the acceleration to go above and below the threshold rapidly and randomly, so the
screen will quickly flip back and forth between the 0° and the 90° orientations. This problem is avoided
in the KXTI9 by choosing a 30° threshold angle. With a 30° threshold, the screen will not rotate from 0°
to 90° until the device is tilted to 60° (30° from 90°). To rotate back to 0°, the user must tilt back to 30°,
thus avoiding the screen flipping problem. This example essentially applies +/- 15° of hysteresis in
between the four screen rotation states. Table 23 shows the acceleration limits implemented for T
=30°.
Orientation X Acceleration (g) Y Acceleration (g)
0°/360°
-0.5 < ax < 0.5
ay > 0.866
90°
ax > 0.866
-0.5 < ay < 0.5
180°
-0.5 < ax < 0.5
ay < -0.866
270°
ax < -0.866
-0.5 < ay < 0.5
Table 23. Acceleration at the four orientations with +/- 15° of hysteresis
The KXTI9 allows the user to change the amount of hysteresis in between the four screen rotation
states. By simply writing to the HYST_SET register, the user can adjust the amount of hysteresis up to
+/- 45°. The plot in Figure 2 shows the typical amount of hysteresis applied for a given digital count
value of HYST_SET.
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
HYST_SET vs Hysteresis
50
45
Hysteresis (+/- degrees)
40
35
30
25
Hysteresis
20
15
10
5
0
0
5
10
15
20
25
30
HYST_SET Value (Counts)
Figure 2. HYST_SET vs Hysteresis
Device Orientation Angle (aka Tilt Angle)
To ensure that horizontal and vertical device orientation changes are detected, even when it isn’t in the
ideal vertical orientation – where the angle θ in Figure 3 is 90°, the KXTI9 considers device orientation
angle in its algorithm.
Angle
Figure 3. Device Orientation Angle
As the angle in Figure 3 is decreased, the maximum gravitational acceleration on the X-axis or Y-axis
will also decrease. Therefore, when the angle becomes small enough, the user will not be able to make
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
the screen orientation change. When the device orientation angle approaches 0° (device is flat on a
desk or table), ax = ay = 0g, az = +1g, and there is no way to determine which way the screen should be
oriented, the internal algorithm determines that the device is in either the face-up or face-down
orientation, depending on the sign of the z-axis. The KXTI9 will only change the screen orientation
when the orientation angle is above the factory-defaulted/user-defined threshold set in the
TILT_ANGLE register. Equation 2 can be used to determine what value to write to the TILT_ANGLE
register to set the device orientation angle.
TILT_ANGLE (counts) = sin θ * (32 (counts/g))
Equation 2. Tilt Angle Threshold
Tilt Timer
The 8-bit register, TILT_TIMER can be used to qualify changes in orientation. The KXTI9 does this by
incrementing a counter with a size that is specified by the value in TILT_TIMER for each set of
acceleration samples to verify that a change to a new orientation state is maintained. A user defined
output data rate (ODR) determines the time period for each sample. Equation 3 shows how to
calculate the TILT_TIMER register value for a desired delay time.
TILT_TIMER (counts) = Delay Time (sec) x ODR (Hz)
Equation 3. Tilt Position Delay Time
Motion Interrupt Feature Description
The Motion interrupt feature of the KXTI9 reports qualified changes in the high-pass filtered acceleration based
on the Wake Up (WUF) threshold. If the high-pass filtered acceleration on any axis is greater than the userdefined wake up threshold (WUF_THRESH), the device has transitioned from an inactive state to an active
state. When configured in the unlatched mode, the KXTI9 will report when the motion event finished and the
device has returned to an inactive state. Equation 4 shows how to calculate the WUF_THRESH register value
for a desired wake up threshold. Note that this calculation varies based on the configured g-range of the part.
WUF_THRESH (counts) = Wake Up Threshold (g) x Sensitivity (counts/g)
Equation 4. Wake Up Threshold
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
A WUF (WUF_TIMER) 8-bit raw unsigned value represents a counter that permits the user to qualify each
active/inactive state change. Note that each WUF Timer count qualifies 1 (one) user-defined ODR period
(OWUF). Equation 5 shows how to calculate the WUF_TIMER register value for a desired wake up delay
time.
WUF_TIMER (counts) = Wake Up Delay Time (sec) x OWUF (Hz)
Equation 5. Wake Up Delay Time
Figure 4 below shows the latched response of the motion detection algorithm with WUF Timer = 10 counts.
Typical Motion Interrupt Example
HPF Acceleration
WUF Threshold
0g
10
WUF Timer
Ex: Delay Counter = 10
Motion
Inactive
Figure 4. Latched Motion Interrupt Response
Figure 5 below shows the unlatched response of the motion detection algorithm with WUF Timer = 10 counts.
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Typical Motion Interrupt Example
HPF Acceleration
WUF Threshold
0g
10
WUF Timer
Ex: Delay Counter = 10
Motion
Inactive
Figure 5. Unlatched Motion Interrupt Response
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Directional Tap Detection Feature Description
The Directional Tap Detection feature of the KXTI9 recognizes single and double tap inputs and reports the
acceleration axis and direction that each tap occurred. Eight performance parameters, as well as a userselectable ODR are used to configure the KXTI9 for a desired tap detection response.
Performance Index
The Directional TapTM detection algorithm uses low and high thresholds to help determine when a tap
event has occurred. A tap event is detected when the previously described jerk summation exceeds
the low threshold (TDT_L_THRESH) for more than the tap detection low limit, but less than the tap
detection high limit as contained in TDT_TAP_TIMER. Samples that exceed the high limit
(TDT_H_THRESH) will be ignored. Figure 6 shows an example of a single tap event meeting the
performance index criteria.
Calculated Performance Index
PI
180
: Sampled Data
160
140
jerk (counts)
120
100
80
60
40
20TDT_L_THRESH
0
3.14
3.15
3.16
3.17
3.18
time(sec)
3.19
3.2
3.21
Figure 6. Jerk Summation vs Threshold
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Single Tap Detection
The latency timer (TDT_LATENCY_TIMER) sets the time period that a tap event will only be
characterized as a single tap. A second tap has to occur outside of the latency timer. If a second tap
occurs inside the latency time, it will be ignored as it occurred too quickly. The single tap will be
reported at the end of the TDT_WINDOW_TIMER. Figure 7 shows a single tap event meeting the PI,
latency and window requirements.
Calculated Performance Index
160
PI
140
TDT_WINDOW_TIMER
120
jerk (counts)
100
TDT_LATENCY_TIMER
80
60
40
TDT_L_THRESH
20
0
2.1
2.2
2.3
2.4
2.5
2.6
2.7
time(sec)
2.8
2.9
3
3.1
Figure 7. Single Directional TapTM Timing
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Double Tap Detection
An event can be characterized as a double tap only if the second tap crosses the performance index
(TDT_L_THRESH) outside the TDT_TIMER. This means that the TDT_TIMER determines the
minimum time separation that must exist between the two taps of a double tap event. Similar to the
single tap, the second tap event must exceed the performance index for the time limit contained in
TDT_TAP_TIMER. The double tap will be reported at the end of the second TDT_LATENCY_TIMER.
Figure 8 shows a double tap event meeting the PI, latency and window requirements.
Calculated Performance Index
PI
TDT_WINDOW_TIMER
200
150
jerk (counts)
TDT_TIMER
100
TDT_LATENCY_TIMER
TDT_LATENCY_TIMER
50
TDT_L_THRESH
0
3.1
3.2
3.3
3.4
3.5
time(sec)
3.6
3.7
3.8
3.9
Figure 8. Double Directional TapTM Timing
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Sample Buffer Feature Description
The sample buffer feature of the KXTI9 accumulates and outputs acceleration data based on how it is
configured. There are 4 buffer modes available, and samples can be accumulated at either low (8-bit) or high
(12-bit) resolution. Acceleration data is collected at the ODR specified by OSAA:OSAD in the Output Data
Control Register. Each buffer mode accumulates data, reports data, and interacts with status indicators in a
slightly different way.
FIFO Mode
Data Accumulation
Sample collection stops when the buffer is full.
Data Reporting
Data is reported with the oldest byte of the oldest sample first (X_L or X based
on resolution).
Status Indicators
A watermark interrupt occurs when the number of samples in the buffer
reaches the Sample Threshold. The watermark interrupt stays active until the
buffer contains less than this number of samples. This can be accomplished
through clearing the buffer or explicitly reading greater than SMPX samples
(calculated with Equation 6).
BUF_RES=0:
SMPX = SMP_LEV[7:0] / 3 – SMP_TH[6:0]
BUF_RES=1:
SMPX = SMP_LEV[7:0] / 6 – SMP_TH[6:0]
Equation 6. Samples Above Sample Threshold
Stream Mode
Data Accumulation
Sample collection continues when the buffer is full; older data is discarded to
make room for newer data.
Data Reporting
Data is reported with the oldest sample first (uses FIFO read pointer).
Status Indicators
A watermark interrupt occurs when the number of samples in the buffer
reaches the Sample Threshold. The watermark interrupt stays active until the
buffer contains less than this number of samples. This can be accomplished
through clearing the buffer or explicitly reading greater than SMPX samples
(calculated with Equation 1).
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
KXTI9-1001
Rev. 3
Dec-2012
Trigger Mode
Data Accumulation
When a physical interrupt is caused by one of the digital engines, the trigger
event is asserted and SMP[6:0] samples prior to the event are retained. Sample
collection continues until the buffer is full.
Data Reporting
Data is reported with the oldest sample first (uses FIFO read pointer).
Status Indicators
When a physical interrupt occurs and there are at least SMP[6:0] samples in the
buffer, BUF_TRIG in BUF_STATUS_REG2 is asserted.
FILO Mode
Data Accumulation
Sample collection continues when the buffer is full; older data is discarded to
make room for newer data.
Data Reporting
Data is reported with the newest byte of the newest sample first (Z_H or Z based
on resolution).
Status Indicators
A watermark interrupt occurs when the number of samples in the buffer
reaches the Sample Threshold. The watermark interrupt stays active until the
buffer contains less than this number of samples. This can be accomplished
through clearing the buffer or explicitly reading greater than SMPX samples
(calculated with Equation 1).
Buffer Operation
The following diagrams illustrate the operation of the buffer conceptually. Actual physical
implementation has been abstracted to offer a simplified explanation of how the different buffer
modes operate. Figure 9 represents a high-resolution 3-axis sample within the buffer. Figures
10-18 represent a 10-sample version of the buffer (for simplicity), with Sample Threshold set to
8.
Regardless of the selected mode, the buffer fills sequentially, one byte at a time. Figure 9
shows one 6-byte data sample. Note the location of the FILO read pointer versus that of the
FIFO read pointer.
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PART NUMBER:
± 2g / 4g / 8g Tri-axis Digital
Accelerometer Specifications
buffer write pointer ---->
Index
0
1
2
3
4
5
6
Byte
X_L
X_H
Y_L
Y_H
Z_L
Z_H
KXTI9-1001
Rev. 3
Dec-2012
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