ADIS16240ABCZ datasheet(14/16 Pages) AD

14 / 16 page

ADIS16240

Rev. 0 | Page 14 of 1

Transient Behavior During Capture

During capture events, the device consumes an increased amount

of current for a short period. Following a capture event, sampling

suspends and the SPI commands are ignored by the sensor for

the pause times that are listed in Table 22.

Table 22. Postcapture Operation Pause Times

Event Length (Samples)

Pause Time (ms)

<64

128

256

512

1024

OPERATIONAL CONTROL

Internal Sample Rate

The SMPL_PRD register (see Table 23) provides a user control

for sample rate adjustment, using the following equation:

fS =

)

(

32768

For example, set SMPL_PRD[7:0] = 0x07 (DIN = 0xC807) to

configure the ADIS16240 to operate at its maximum sample

rate of 4096 SPS. Note that the sample rate affects power dis-

sipation and peak resolution during event capture.

Table 23. SMPL_PRD Register Bit Descriptions1

Bit

Description (Default = 0x001F)

[15:0]

Sample rate scale factor, binary format (NSR)

1 The SMPL_PRD register is located at Address 0x49[15:8] and Address 0x48[7:0].

Global Commands

For convenience, the GLOB_CMD register (see Table 24) provides

an array of single-write commands. Setting the assigned bit to 1

activates each function, right after the 16th SCLK in the SPI com-

munication sequence. When the function completes, the bit

restores itself to 0. All commands in the GLOB_CMD register

require the power supply to be within normal limits for the

execution times listed in Table 24. The execution times reflect the

factory default configuration, where applicable, and describe the

time required to return to normal operation. For example, set

GLOB_CMD[2] = 1 (DIN = 0xCA04) to place the part in standby

mode. Set GLOB_CMD[8] = 1 (DIN = 0xCB01) to wake up the

device and return to normal operation.

Input/Output Lines

The ADIS16240 provides two general-purpose digital input/

output lines that offer several functions. When using the factory-

default configuration, MSC_CTRL[2:0] establishes DIO1 as

a positive data-ready output. Change MSC_CTRL[2:0] to 100

(DIN = 0xC604) to make DIO1 a negative data-ready output

signal. ALM_CTRL[2:0] offers a control for setting one of the

digital signals as an alarm indicator. For example, set ALM_

CTRL[2:0] = 110 (DIN = 0xBC06) to set DIO1 as a positive

alarm indicator output signal. When configured as general-

purpose lines, the GPIO_CTRL register configures DIO1 and

DIO2. For example, set GPIO_CTRL = 0x0103 (DIN = 0xC403,

then 0xC501) to set DIO1 and DIO2 as outputs, with DIO1 in

a 1 state and DIO2 in a 0 state. In the event of competing assign-

ments, the order of precedence is MSC_CTRL, ALM_CTRL,

and GPIO_CTRL.

Table 24. GLOB_CMD Register Bit Descriptions1

Bit

Description

Execution Time2

[15:9]

Unused

N/A

Wake up from standby mode

0.2 ms

Software reset

32 ms

Clear capture buffer flash memory

350 ms

Clear peak registers

N/A

Clear DIAG_STAT register

N/A

Save configuration to flash

24 ms

Start standby mode for low power

N/A

Restore factory-default settings

350 ms

Auto-null

N/A

1 The GLOB_CMD register is located at Address 0x4B[15:8] and Address 0x4A[7:0].

2 SPI processing and data sampling suspend for the indicated times.

Table 25. MSC_CTRL Register Bit Descriptions1

Bit

Description (Default = 0x0006)

Enables sum-of-squares output (XYZPEAK_OUT)

Enables peak tracking output (XPEAK_OUT,

YPEAK_OUT, and ZPEAK_OUT)

[13:10]

Unused

No self-test on startup when set to 1

Self-test enable: 1 = apply electrostatic force, 0 = disabled

[7:3]

Unused

Data-ready enable: 1 = enabled, 0 = disabled

Data-ready polarity: 1 = active high, 0 = active low

Data-ready line selection: 1 = DIO2, 0 = DIO1

1 The MSC_CTRL register is located at Address 0x47[15:8] and Address 0x46[7:0].

Table 26. GPIO_CTRL Register Bit Descriptions1

Bit

Description (Default = 0x0000)

[15:10]

Unused

General-Purpose I/O Line 2 data level

General-Purpose I/O Line 1 data level

[7:2]

Unused

General-Purpose I/O Line 2, data direction control:

1 = output, 0 = input

General-Purpose I/O Line 1, data direction control:

1 = output, 0 = input

1 The GPIO_CTRL register is located at Address 0x45[15:8] and Address 0x44[7:0].

Offset Adjustment

The XACCL_OUT, YACCL_OFF, and ZACCL_OFF registers

add to the sensor outputs and provide a convenient offset adjust-

ment function for each accelerometer output. For example, writing

0x0A to YACCL_OUT[7:0] (DIN = 0xA20A) results in a 514 mg

offset adjustment for the YACCL_OUT output data.

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