Sensor

Freescale Semiconductor, Inc.

43

MMA65xx

3.10

Device Initialization

Following power-up, under-voltage reset, or a SPI reset command sequence, the device proceeds through an internal initial-

ization process as shown below. Figure 34 also shows the device performance for an example external system level initialization

procedure.

Figure 34. Initialization Process

Dly

POR

OTP Copy to

Mirror Registers

Offset Cancellation

Startup Phase 2

Initialize R/W

Registers to

Desired State

Verify X-Axis

Offset

Verify X-Axis

Self Test &

ARM_X Asserted

Verify Y-Axis

Offset & ARM_Y

DeAsserted

Verify X-Axis

Offset & ARM_X

DeAsserted

Verify Y-Axis

Self Test &

ARM_Y Asserted

Verify X-Axis

Offset & ARM_X

DeAsserted

Verify Y-Axis

Offset & ARM_Y

DeAsserted

Offset Cancellation

Startup Phase 1

Offset Cancellation

Startup Phase 3

Offset Cancellation

Normal Mode

Ready for SPI

Command

ENDINIT Clear

Dly

Dly

Dly

Re-Initialize

R/W Registers

(if needed)

Activate

X-Axis

Self Test

Internal

Offset Error

Corrected to ‘0’

DeActivate

X-Axis

Self Test

Activate

Y-Axis

Self Test

DeActivate

Y-Axis

Self Test

Normal

Mode

Internal Initialization

External Initialization

Delay

DeAssertion

Dependent on Pulse

Stretch and/or Arming Mode

DeAssertion

Dependent on Pulse

Stretch and/or Arming Mode

Assertion

Dependent on

Arming Mode

Assertion

Dependent on

Arming Mode

Set ENDINIT

Read DEVSTAT

to clear flags

Re-read DEVSTAT

to verify Status

and

X_ST

Y_ST

X_ARM

Y_ARM

Notes:1) X-Axis and Y-Axis Self Test can be enabled and evaluated simultaneously to reduce test time.

For failure mode coverage of the arming pins and of potential common axis failures, Freescale recommends independent self test activation.