Datasheet
Sensors
NXP Semiconductors 41
MMA8452Q
ACTIVE bit selects between standby mode and active mode. The default value is 0 for standby mode.
LNOISE bit selects between normal full dynamic range mode and a high sensitivity, low noise mode. In low noise mode, the
maximum signal that can be measured is ±4 g. Note: Any thresholds set above 4 g will not be reached.
F_READ bit selects between normal and fast-read mode. When selected, the auto-increment counter will skip over the LSB data
bytes.
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].
Table 56. Full-scale selection
Active Mode
0 Standby
1Active
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
Field 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
00 Normal
0 1 Low Noise Low Power
1 0 High Resolution
1 1 Low Power