MMA7455L Просмотр технического описания (PDF) - Freescale Semiconductor
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MMA7455L Datasheet PDF : 35 Pages
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PULSE DETECTION
In Pulse Mode, all functions can be active including measurements, level detections and pulse detection. There are two interrupt
pins available for detection of level and pulse conditions. The pulse detection has several timing windows associated with it. A
single pulse and a double pulse can be detected. Also freefall can be detected. The interrupt pins can be assigned to detect the
first pulse on one interrupt and the second pulse on the other interrupt. This is explained on Page 15, under the Assigning, Clear-
ing & Detecting Interrupts section.
By default all three axes are enabled and the detection range is 8g only. X and/or Y and/or Z can be disabled. There is a choice
between doing a detection for Motion detection vs. doing a detection for Freefall.
$18: Control 1 (Read/Write): Disable X, Y or Z for Pulse Detection
This allows the user to define how many axes to use for detection. All axes are enabled by default. To disable write 1
XDA: Disable X
YDA: Disable Y
ZDA: Disable Z.
D7
DFBW
0
D6
THOPT
0
D5
ZDA
0
D4
YDA
0
D3
XDA
0
D2
INTREG[1]
0
D1
INTREG[0]
0
D0
INTPIN
0
Reg $18
Function
Default
$19: Control 2 (Read/Write): Motion Detection (OR condition) or Freefall Detection (AND condition)
PDPL
0: Pulse detection polarity is positive and detecting condition is OR 3 axes.
1: Pulse detection polarity is negative and detecting condition is AND 3 axes.
D7
D6
D5
D4
D3
D2
D1
D0
--
--
--
--
--
DRVO
PDPL
LDPL
0
0
0
0
0
0
0
0
Reg $19
Function
Default
CASE 1: Single Pulse Motion Detection: X or Y or Z > Pulse Threshold for Time < Pulse Duration
For motion detection with single 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. 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
MMA7455L
12
Sensors
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