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ADXL345 Data Sheet

DATA FORMATTING OF UPPER DATA RATES

Formatting of output data at the 3200 Hz and 1600 Hz output

data rates changes depending on the mode of operation (full-

resolution or fixed 10-bit) and the selected output range.

When using the 3200 Hz or 1600 Hz output data rates in full-

resolution or ±2 g, 10-bit operation, the LSB of the output data-

word is always 0. When data is right justified, this corresponds

to Bit D0 of the DATAx0 register, as shown in Figure 49. When

data is left justified and the part is operating in ±2 g, 10-bit mode,

the LSB of the output data-word is Bit D6 of the DATAx0 register.

In full-resolution operation when data is left justified, the location

of the LSB changes according to the selected output range.

For a range of ±2 g, the LSB is Bit D6 of the DATAx0 register;

for ±4 g, Bit D5 of the DATAx0 register; for ±8 g, Bit D4 of the

DATAx0 register; and for ±16 g, Bit D3 of the DATAx0 register.

This is shown in Figure 50.

The use of 3200 Hz and 1600 Hz output data rates for fixed 10-

bit operation in the ±4 g, ±8 g, and ±16 g output ranges

provides an LSB that is valid and that changes according to the

applied acceleration. Therefore, in these modes of operation, Bit

D0 is not always 0 when output data is right justified and Bit D6

is not always 0 when output data is left justified. Operation at

any data rate of 800 Hz or lower also provides a valid LSB in all

ranges and modes that changes according to the applied

acceleration.

D1D2D3D4D5D6D7

D0D1D2D3D4D5D6D7

DATAx1 REGISTER DATAx0 REGISTER

OUTPUT DATA-WORD FOR

±16g, FULL-RESOLUTION MODE.

OUTPUT DATA-WORD FOR ALL

10-BIT MODES AND THE ±2g,

FULL-RESOLUTION MODE.

THE ±4g AND ±8g FULL-RESOLUTION MODES HAVE THE SAME LSB LOCATION AS THE ±2g

AND ±16g FULL-RESOLUTION MODES, BUT THE MSB LOCATION CHANGES TO BIT D2 AND

BIT D3 OF THE DATAX1 REGISTER FOR ±4g AND ±8g, RESPECTIVELY.

07925-145

Figure 49. Data Formatting of Full-Resolution and ±2 g, 10-Bit Modes of Operation When Output Data Is Right Justified

0D1D2D3D4D5D6D7

D0D1D2D3D4D5D6D7

DATAx1 REGISTER DATAx0 REGISTER

MSB FOR ALL MODES

OF OPERATION WHEN

LEFT JUSTIFIED.

LSB FOR ±2g, FULL-RESOLUTION

AND ±2g, 10-BIT MODES.

LSB FOR ±4g, FULL-RESOLUTION MODE.

LSB FOR ±8g, FULL-RESOLUTION MODE.

LSB FOR ±16g, FULL-RESOLUTION MODE.

FOR 3200Hz AND 1600Hz OUTPUT DATA RATES, THE LSB IN THESE MODES IS ALWAYS 0.

ADDITIONALLY, ANY BITS TO THE RIGHT OF THE LSB ARE ALWAYS 0 WHEN THE OUTPUT

DATA IS LEFT JUSTIFIED.

07925-146

Figure 50. Data Formatting of Full-Resolution and ±2 g, 10-Bit Modes of Operation When Output Data Is Left Justified

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