Sensor

16

Freescale Semiconductor, Inc.

MMA65xx

3.1.6.3

End of Initialization Bit (ENDINIT)

The ENDINIT bit is a control bit used to indicate that the user has completed all device and system level initialization tests,

and that the device will operate in normal mode. Once the ENDINIT bit is set, writes to all writable register bits are inhibited except

for the DEVCTL register. Once written, the ENDINIT bit can only be cleared by a device reset. The writable register CRC check

(reference Section 3.2.2) is only enabled when the ENDINIT bit is set.

When ENDINIT is set, the following occurs:

•

Offset Cancellation is forced to normal mode. OCPHASE[1:0], and OFFCFG_EN remain in their previously set states.

•

X-Axis Self Test is disabled. ST_X remains in its previously set states.

•

Y-Axis Self Test is disabled. ST_Y remains in its previously set states.

3.1.6.4

SD Bit

The SD bit determines the format of acceleration data results. If the SD bit is set to a logic ‘1’, unsigned results are transmitted,

with the zero-g level represented by a nominal value of 512. If the SD bit is cleared, signed results are transmitted, with the zero-

g level represented by a nominal value of 0.

3.1.6.5

OFMON Bit

The OFMON bit determines if the offset monitor circuit is enabled. If the OFMON bit is set to a logic ‘1’, the offset monitor is

enabled. Reference Section 3.8.5. If the OFMON bit is cleared, the offset monitor is disabled.

If the OC bit in the DEVCFG register is cleared (Offset Cancelled Data), then the Offset Monitor is automatically enabled (OF-

MON = ‘1’) regardless of the value written to DEVCFG[3].

3.1.6.6

ARM Configuration Bits (A_CFG[2:0])

The ARM Configuration Bits (A_CFG[2:0]) select the mode of operation for the ARM_X/PCM_X, ARM_Y/PCM_Y pins.

SD

Operating Mode

1

Unsigned Data Output

0

Signed Data Output

OFMON

Operating Mode

1

Offset Monitor Circuit Enabled

0

Offset Monitor Circuit Disabled

Table 9. Arming Output Configuration

A_CFG[2]

A_CFG[1]

A-CFG[0]

Operating Mode

Output Type

Reference

0

0

0

Arm Output Disabled

Hi Impedance

0

0

1

PCM Output

Digital Output

Section 3.8.11

0

1

0

Moving Average Mode

Active High with Pulldown Current

Section 3.8.10.1

0

1

1

Moving Average Mode

Active Low with Pullup Current

Section 3.8.10.1

1

0

0

Count Mode

Active High with Pulldown Current

Section 3.8.10.2

1

0

1

Count Mode

Active Low with Pullup Current

Section 3.8.10.2

1

1

0

Unfiltered Mode

Active High with Pulldown Current

Section 3.8.10.3

1

1

1

Unfiltered Mode

Active Low with Pullup Current

Section 3.8.10.3