MMA8450QT datasheet(21/57 Pages) FREESCALE

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Sensors

Freescale Semiconductor

MMA8450Q

6.1

Data Registers

The following are the data registers for the MMA8450Q. For more information on data manipulation of the MMA8450Q, refer

to application note, AN3922.

0x00, 0x04, 0x0B: STATUS Registers

When FDE bit found in register 0x16 (XYZ_DATA_CFG), bit 7 is cleared (the FIFO is not on) register 0x00, 0x04 and 0x0B

should all be the same value and reflect the real-time status information of the X, Y and Z sample data. When FDE is set (the

FIFO is on) Register 0x00, 0x04 and 0x10 will have the same value and 0x0B will reflect the status of the transient data. The

aliases allow the STATUS register to be read easily before reading the current 8-bit, 12-bit, or FIFO sample data using the register

address auto-incrementing mechanism.

ZYXOW is set whenever a new acceleration data is produced before completing the retrieval of the previous set. This event

occurs when the content of at least one acceleration data register (i.e., OUTX, OUTY, OUTZ) has been overwritten. ZYXOW is

cleared when the high-bytes of the acceleration data (OUTX_MSB, OUTY_MSB, OUTZ_MSB) of all the active channels are read.

ZOW is set whenever a new acceleration sample related to the Z-axis is generated before the retrieval of the previous sample.

When this occurs the previous sample is overwritten. ZOW is cleared anytime OUTZ_MSB register is read.

YOW is set whenever a new acceleration sample related to the Y-axis is generated before the retrieval of the previous sample.

When this occurs the previous sample is overwritten. YOW is cleared anytime OUTY_MSB register is read.

XOW is set whenever a new acceleration sample related to the X-axis is generated before the retrieval of the previous sample.

When this occurs the previous sample is overwritten. XOW is cleared anytime OUTX_MSB register is read.

ZYXDR signals that a new sample for any of the enabled channels is available. ZYXDR is cleared when the high-bytes of the

acceleration data (OUTX_MSB, OUTY_MSB, OUTZ_MSB) of all the enabled channels are read.

ZDR is set whenever a new acceleration sample related to the Z-axis is generated. ZDR is cleared anytime OUTZ_MSB register

is read. In order to enable the monitoring and assertion of this bit, the ZDR bit requires the Z-axis event detection flag to be

enabled (bit ZDEFE = 1 inside XYZ_DATA_CFG register).

Alias for DR_Status (0x0B) or F_Status (0x10) (Read Only)

FDE (FIFO Data Enable Bit 7, Reg 0x16) Setting

Alias Status

FDE = 0

0x00 = 0x04 = DR_STATUS (0x0B)

FDE = 1

0x00 = 0x04 = F_STATUS (0x10)

0X00, 0X04, 0X0B STATUS: Data Status Registers (Read Only)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

ZYXOW

ZOW

YOW

XOW

ZYXDR

ZDR

YDR

XDR

Table 12. STATUS Description

ZYXOW

X, Y, Z-axis Data Overwrite. Default value: 0

0: No data overwrite has occurred

1: Previous X, Y, or Z data was overwritten by new X, Y, or Z data before it was read

ZOW

Z-axis Data Overwrite. Default value: 0

0: No data overwrite has occurred

1: Previous Z-axis data was overwritten by new Z-axis data before it was read

YOW

Y-axis Data Overwrite. Default value: 0

0: No data overwrite has occurred

1: Previous Y-axis data was overwritten by new Y-axis data before it was read

XOW

X-axis Data Overwrite. Default value: 0

0: No data overwrite has occurred

1: Previous X-axis data was overwritten by new X-axis data before it was read

ZYXDR

X, Y, Z-axis new Data Ready. Default value: 0

0: No new set of data ready

1: A new set of data is ready

ZDR

Z-axis new Data Available. Default value: 0

0: No new Z-axis data is ready

1: A new Z-axis data is ready

YDR

Z-axis new Data Available. Default value: 0

0: No new Y-axis data ready

1: A new Y-axis data is ready

XDR

Z-axis new Data Available. Default value: 0

0: No new X-axis data ready

1: A new X-axis data is ready

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