Sensors

4

Freescale Semiconductor, Inc.

MPL115A2

3

Overview of Functions/Operation

Figure 2. Sequence Flow Chart

usage sequence is as follows:

Initial Power-up

standby mode.

Reading Coefficient Data

The user then typically accesses the part and reads the coefficient data. The main circuits within the slave device are disabled

during read activity. The coefficients are usually stored in the host microcontoller local memory but can be re-read at any time.

It is not necessary to read the values stored in the host microcontroller multiple times because the coefficients within a device

are constant and do not change. However, note that the coefficients will be different from device to device, and cannot be used

for another part.

Data Conversion

This is the first step that is performed each time a new pressure reading is required which is initiated by the host sending the

CONVERT command. The main system circuits are activated (wake) in response to the command and after the conversion

completes, the result is placed into the Pressure and Temperature ADC output registers.

device then enters standby mode.

Compensated Pressure Reading

After the conversion has been given sufficient time to complete, the host microcontroller reads the result from the ADC output

registers and calculates the Compensated Pressure, a barometric/atmospheric pressure value which is compensated for

changes in temperature and pressure sensor linearity. This is done using the coefficient data from the MPL115A and the raw

sampled pressure and temperature ADC output values, in a compensation equation (detailed later). Note that this is an absolute

pressure measurement with a vacuum as a reference.

From this step the host controller may either wait and then return to the Data Conversion step to obtain the next pressure reading

or it may go to the Shutdown step.

Reading

coefficient data

Data conversion

Initial

powerup

Compensated

pressure reading

Shutdown