AN 009
Register Recommendations
CTRL_REGB
CLKhld ENABLE
ST
X
X
X
FFIen
XI
0
1
0
0
0
0
1
0
Figure 4. Operational Starting Point for CTRL_REGB
CLKhld = 0: The KXPS5 will not hold the I2C clock during A/D conversions.
ENABLE = 1: The KXPS5 is enabled/operational.
ST = 0: The KXPS5 self-test function is not enabled/operational.
FFIen = 1: Free-fall detection interrupt is enabled/operational.
CTRL_REGC
X
X
X
FFLatch MOTLatch
X
IntSpd1 IntSpd0
0
0
0
0
0
0
0
0
Figure 5. Operational Starting Point for CTRL_REGC
FFLatch = 0: The free-fall interrupt output will go high whenever the criterion for free-fall
detection is met. The output will return low when the criterion is not met.
MOTLatch = 0: The motion interrupt output will go high whenever the criterion for motion
detection is met. The output will return low when the criterion is not met.
IntSpd1 and IntSpd0 = 0: The interrupt sampling frequency is 250 samples/second.
Therefore, the interrupt delay times can be calculated using Equation 1.
Free-fall Delay (sec) = FF_Delay (# of samples) / 250 (samples/sec)
High-g Motion Delay (sec) = MOT_Delay (# of samples) / 250 (samples/sec)
Equation 1. Free-fall and Motion Delay Calculations
Thresholds and Delays
The following are some suggested acceleration thresholds and delay (or dwell) times
appropriate for many HDD protection applications. For each suggested parameter the
appropriate register value is provided in binary and hexadecimal.
Free fall
Detection Threshold = 0.4g
FF_INT = (0000 1110 or 0x0E)
Delay Time = 80mS
FF_DELAY = (0001 0100 or 0x14)
High-g Motion
Detection Threshold = 2.5g
© Kionix 2006
9 March 2006
Page 4 of 6
MOT_INT = (0101 0101 or 0x55)
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