Freescale Semiconductor Energy Efficient Solutions Xtrinsic MMA8452Q, Data Sheet: Technical Data

Page: 38 / 50

MMA8452Q
Sensors
38 Freescale Semiconductor, Inc.
0x2B: CTRL_REG2 System Control 2 Register
ST bit activates the self-test function. When ST is set, X, Y, and Z outputs will shift. RST bit is used to activate the software reset.
The reset mechanism can be enabled in STANDBY and ACTIVE mode.
When the reset bit is enabled, all registers are rest and are loaded with default values. Writing ‘1’ to the RST bit immediately
resets the device, no matter whether it is in ACTIVE/WAKE, ACTIVE/SLEEP, or STANDBY mode.
The I
2
C communication system is reset to avoid accidental corrupted data access.
At the end of the boot process the RST bit is deasserted to 0. Reading this bit will return a value of zero.
The (S)MODS[1:0] bits select which Oversampling mode is to be used shown in Table 58 . The Oversampling modes are
available in both WAKE Mode MOD[1:0] and also in the SLEEP Mode SMOD[1:0].
0x2B: CTRL_REG2 Register (Read/Write)
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
ST RST 0 SMODS1 SMODS0 SLPE MODS1 MODS0
Table 57. CTRL_REG2 Description
ST
Self-Test Enable. Default value: 0.
0: Self-Test disabled; 1: Self-Test enabled
RST
Software Reset. Default value: 0.
0: Device reset disabled; 1: Device reset enabled.
SMODS[1:0]
SLEEP mode power scheme selection. Default value: 00.
See Table 58 and Table 59
SLPE
Auto-SLEEP enable. Default value: 0.
0: Auto-SLEEP is not enabled;
1: Auto-SLEEP is enabled.
MODS[1:0]
ACTIVE mode power scheme selection. Default value: 00.
See Table 58 and Table 59
Table 58. MODS Oversampling Modes
(S)MODS1 (S)MODS0 Power Mode
0 0 Normal
0 1 Low Noise Low Power
1 0 High Resolution
1 1 Low Power
Table 59. MODS Oversampling Modes Current Consumption and Averaging Values at each ODR
Mode Normal (00) Low Noise Low Power (01) High Resolution (10) Low Power (11)
ODR Current
μ
A OS Ratio Current
μ
A OS Ratio Current
μ
A OS Ratio Current
μ
A OS Ratio
1.56 Hz 24 128 8 32 165 1024 6 16
6.25 Hz 24 32 8 8 165 256 6 4
12.5 Hz 24 16 8 4 165 128 6 2
50 Hz 24 4 24 4 165 32 14 2
100 Hz 44 4 44 4 165 16 24 2
200 Hz 85 4 85 4 165 8 44 2
400 Hz 165 4 165 4 165 4 85 2
800 Hz 165 2 165 2 165 2 165 2