MPL115A1 Просмотр технического описания (PDF) - Freescale Semiconductor

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MPL115A1

Miniature SPI Digital Barometer

Freescale Semiconductor 

The polynomial can be evaluated (Equation 1) as a sequence of 3 MACs:

Pcomp = a0 + (b1 + c12 ⋅ Tadc) ⋅ Padc + b2 ⋅ Tadc

b1

c12

a1

Tadc

a0

y1

Padc

b2

Tadc

y

PComp

Please refer to Freescale application note AN3785 for more detailed notes on implementation.

3.4 SPI Device Read/Write Operations

All device read/write operations are memory mapped. Device actions e.g. “Start Conversions” are controlled by writing to the

appropriate memory address location. All memory address locations are 6-bit (see Table 2).

The 8-bit command word comprises:

• the most significant bit which is the Read/Write identifier which is '1' for read operations and '0' for write operations.

• the 6-bit address (from Table 2);

• the least significant bit which is not used and is don't care (X).

The device write commands are shown in Table 3.

Table 3. SPI Write Command

Start Conversions

Command

Binary

0010010X

HEX(1)

0x24

X = don’t care

1. The command byte needs to be paired with a 0x00 as part of the SPI exchange to complete the passing of Start

Conversions.

The actions taken by the part in response to each command are as follows:

Table 4. SPI Write Command Description

Command

Start Conversions

Action Taken

Wake main circuits. Start clock. Allow supply stabilization time. Select pressure sensor input.

Apply positive sensor excitation and perform A to D conversion. Select temperature input.

Perform A to D conversion. Load the Pressure and Temperature registers with the result. Shut

down main circuits and clock.

Sensors

Freescale Semiconductor, Inc.

MPL115A1

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