Sensors

Freescale Semiconductor

13

MMA7455L

Figure 4. Single Pulse Detection

CASE 2: Freefall Detection: X and Y and Z < Pulse Threshold for Time > Latency Time

For freefall detection, set in pulse mode. PDPL in Register $19 =1 for “AND” freefall condition. The Pulse threshold must be set

in Register $1B and the pulse latency time window must also be set using Register $1D. All three axes must remain below the

threshold longer than the time window for the interrupt to trigger.

Figure 5. Freefall Detection in Pulse Mode

$1B: Pulse Detection Threshold Limit Value (Read/Write)

D7

D6

D5

D4

D3

D2

D1

D0

Reg $1B

PDTH[7]

PDTH[6]

PDTH[5]

PDTH[4]

PDTH[3]

PDTH[2]

PDTH[1]

PDTH[0]

Function

00

00

00

00

Default

$1D: Latency Time Value (Read/Write)

D7

D6

D5

D4

D3

D2

D1

D0

Reg $1D

LT[7]

LT[6]

LT[5]

LT[4]

LT[3]

LT[2]

LT[1]

LT[0]

Function

000000

01

Default

Pulse Detection

Time duration

G

th

G

INT pin

Time

Time

Single Pulse Detection ($19 PDPL=0 indicating motion detection)

*Note there is up to

1.6ms delay on the

interrupt signal