MMA7455L 데이터 시트보기 (PDF) - Freescale Semiconductor
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MMA7455L Datasheet PDF : 35 Pages
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CASE 3: Double Pulse Detection: X OR Y OR Z > Threshold for Pulse Duration1 < PDTime1, Latency Time, AND
X OR Y OR Z > Threshold for Pulse Duration2 < PDTime2
For motion detection with double pulse the device must be in pulse mode. PDPL in Register $19 =0 for “OR” motion condition.
The Pulse Threshold must be set in Register $1B and the Pulse Duration Time Window must also be set using Register $1C.
Then the Latency Time (time between pulses) must be set in Register $1D and then the Second Time Window must be set in
Register $1E for the time window of the second pulse. The pulse must be detected before the time window closes for the interrupt
to trigger.
$1B: Pulse Detection Threshold Limit Value (Read/Write)
D7
D6
D5
D4
D3
PDTH[7]
PDTH[6]
PDTH[5]
PDTH[4]
PDTH[3]
0
0
0
0
0
D2
PDTH[2]
0
D1
PDTH[1]
0
D0
PDTH[0]
0
Reg $1B
Function
Default
$1C: Pulse Duration Value (Read/Write)
D7
D6
D5
PD[7]
PD[6]
PD[5]
0
0
0
D4
PD[4]
0
D3
PD[3]
0
D2
PD[2]
0
D1
PD[1]
0
D0
PD[0]
1
Reg $1C
Function
Default
$1D: Latency Time Value (Read/Write)
D7
D6
D5
D4
LT[7]
LT[6]
LT[5]
LT[4]
0
0
0
0
$1E: Time Window for 2nd Pulse Value (Read/Write)
D7
D6
D5
D4
TW[7]
TW[6]
TW[5]
TW[4]
0
0
0
0
D3
LT[3]
0
D3
TW[3]
0
D2
LT[2]
0
D2
TW[2]
0
D1
LT[1]
0
D1
TW[1]
0
D0
LT[0]
1
D0
TW[0]
0
Reg $1D
Function
Default
Reg $1E
Function
Default
When any of the events are detected, the interrupt pin (either INT1 or INT2) will go high. The interrupt pin assignment is set
up in Register $18, discussed in the Assigning, Clearing & Detecting Interrupts section on Page 15. The detection status is
monitored by the detection source register $0A.
G
Pulse Detection
Time Window
Pulse Detection Time Window for
2nd pulse
Gt h
Detection Source
Register
Latency Time Window
(2nd pulse ignored here)
PDX or PDY or PDZ bit in Detection
source register is set.
Time
*Note th ere is up to 1.6ms
delay on the interrupt signal
INT
Time
Time Window >0 for 2 pulse detect
*Note there is up to 1.6ms
delay on the interrupt sign al
Double Pulse Detection ($19 PDPL=0 indicating motion detection)
Time Window for 2nd pulse $1E TW>0 indicating double pulse
Figure 6. Double Pulse Detection
Time
MMA7455L
14
Sensors
Freescale Semiconductor
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