ADIS16240ABCZ datasheet(9/16 Pages) AD

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ADIS16240

Rev. 0 | Page 9 of

BASIC OPERATION

The ADIS16240 starts up automatically when it has a valid power

supply and begins producing digital acceleration data in the output

registers. When using the factory-default configuration, DIO1

serves as a data-ready indicator signal that can drive a processor

interrupt function. Figure 14 shows a schematic for connecting

to a SPI-compatible processor platform, referred to as the SPI

master.

ADIS16240

SPI SLAVE

SCLK

DIN

DOUT

DIO1

DIO2

VDD

SYSTEM PROCESSOR

SPI MASTER

SCLK

MOSI

MISO

IRQ1

IRQ2

Figure 14. Electrical Hook-Up Diagram

Table 5. Generic Master Processor Pin Names and Functions

Pin Name

Function

Slave select.

IRQ1, IRQ2

Interrupt request inputs.

MOSI

Master output, slave input.

MISO

Master input, slave output.

SCLK

Serial clock.

The ADIS16240 SPI interface supports full duplex serial commu-

nication (simultaneous transmit and receive) and uses the bit

sequence shown in Figure 18. Processor platforms typically support

SPI communication with general-purpose serial ports that require

some configuration in their control registers. Table 6 lists the most

common settings that require attention when initializing a pro-

cessor serial port for communication with the ADIS16240.

Table 6. Generic Master Processor SPI Settings

Processor Setting

Description

Master

The ADIS16240 operates as a slave.

SCLK Rate ≤ 2.5 MHz

Bit rate setting.

SPI Mode 3 (1,1)

Clock polarity/phase (CPOL = 1, CPHA = 1).

MSB First

Bit sequence.

16-Bit

Shift register/data length.

User registers govern all data collection and configuration. Table 7

provides a memory map that includes all user registers, along with

references to bit assignment tables that follow the generic assign-

ments in Figure 15.

UPPER BYTE

LOWER BYTE

Figure 15. Generic Register Bit Assignments

SPI Write Commands

Master processors write to the control registers, one byte at a

time, using the bit assignments shown in Figure 18. The program-

mable registers in Table 7 provide controls for optimizing sensor

operation and for starting various automated functions. For

example, set GLOB_CMD[8] = 1 (DIN = 0xCB01) to wake up the

device.

DIN

SCLK

Figure 16. SPI Sequence for a Wake-Up Command (DIN = 0xCB01)

Some configurations require writing both bytes to a register,

which takes two separate 16-bit sequences. See GLOB_CMD[3]

in Table 24 for backing up configuration data in nonvolatile

flash memory.

SPI Read Commands

Reading data on the SPI requires two consecutive 16-bit

sequences. The first sequence transmits the read command on

DIN, and the second sequence receives the resulting data from

DOUT. The 7-bit register address can represent either the upper

or lower byte address for the target register. For example, DIN

can be either 0x0200 or 0x0300 when reading the SUPPLY_OUT

the master processor can read the output data from DOUT while

using the same SCLK pulses to transmit a new command on

DIN. In Figure 17, the second SPI segment sets up the device to

read YACCL_OUT on the following SPI segment (not shown).

DIN

SCLK

DIN = 0x0400 PRODUCES XACCL_OUT CONTENTS ON

DOUT DURING THE NEXT SPI SEGMENT

DOUT

SPI SEGMENT 1

SPI SEGMENT 2

DOUT = 0x802B = 2.21g, NEW DATA

DIN = 0x0600 TO READ YACCL_OUT

Figure 17. Example SPI Read Sequence

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