ADIS16488 datasheet(30/36 Pages) AD

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ADIS16488

Data Sheet

Rev. B | Page 30 of 36

Table 117. FNCTIO_CTRL (Page 3, Base Address = 0x06)

Bits

Description (Default = 0x000D)

[15:12]

Not used

Alarm indicator: 1 = enabled, 0 = disabled

Alarm indicator polarity: 1 = positive, 0 = negative

[9:8]

Alarm indicator line selection:

00 = DIO1, 01 = DIO2, 10 = DIO3, 11 = DIO4

Sync clock input enable: 1 = enabled, 0 = disabled

Sync clock input polarity:

1 = rising edge, 0 = falling edge

[5:4]

Sync clock input line selection:

00 = DIO1, 01 = DIO2, 10 = DIO3, 11 = DIO4

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

Data-ready polarity: 1 = positive, 0 = negative

[1:0]

Data-ready line selection:

00 = DIO1, 01 = DIO2, 10 = DIO3, 11 = DIO4

Data-Ready Indicator

FNCTIO_CTRL[3:0] provide some configuration options for

using one of the DIOx lines as a data-ready indicator signal,

which can drive a processor’s interrupt control line. The factory

default assigns DIO2 as a positive polarity, data-ready signal.

Use the following sequence to change this assignment to DIO1

with a negative polarity: turn to Page 3 (DIN = 0x8003) and set

FNCTIO_CTRL[3:0] = 1000 (DIN = 0x8608, then DIN = 0x8700).

The timing jitter on the data-ready signal is ±1.4 µs.

Input Sync/Clock Control

FNCTIO_CTRL[7:4] provide some configuration options for

using one of the DIOx lines as an input synchronization signal

for sampling inertial sensor data. For example, use the following

sequence to establish DIO4 as a positive polarity, input clock pin

and keep the factory default setting for the data-ready function:

turn to Page 3 (DIN = 0x8003) and set FNCTIO_CTRL[7:0]

= 0xFD (DIN = 0x86FD, then DIN = 0x8700). Note that this

command also disables the internal sampling clock, and no

data sampling takes place without the input clock signal.

When selecting a clock input frequency, consider the 330 Hz

sensor bandwidth, because under sampling the sensors can

degrade noise and stability performance.

General-Purpose I/O Control

When FNCTIO_CTRL does not configure a DIOx pin,

GPIO_CTRL provides register controls for general-purpose use

of the pin. GPIO_CTRL[3:0] provides input/output assignment

controls for each line. When the DIOx lines are inputs, monitor

their level by reading GPIO_CTRL[7:4]. When the DIOx lines

are used as outputs, set their level by writing to GPIO_CTRL[7:4].

For example, use the following sequence to set DIO1 and

DIO3 as high and low output lines, respectively, and set DIO2

and DIO4 as input lines. Turn to Page 3 (DIN = 0x8003) and set

GPIO_CTRL[7:0] = 0x15 (DIN = 0x8815, then DIN = 0x8900).

Table 118. GPIO_CTRL (Page 3, Base Address = 0x08)

Bits

Description (Default = 0x00X0)1

[15:8]

Don’t care

General-Purpose I/O Line 4 (DIO4) data level

General-Purpose I/O Line 3 (DIO3) data level

General-Purpose I/O Line 2 (DIO2) data level

General-Purpose I/O Line 1 (DIO1) data level

General-Purpose I/O Line 4 (DIO4) direction control

(1 = output, 0 = input)

General-Purpose I/O Line 3 (DIO3) direction control

(1 = output, 0 = input)

General-Purpose I/O Line 2 (DIO2) direction control

(1 = output, 0 = input)

General-Purpose I/O Line 1 (DIO1) direction control

(1 = output, 0 = input)

GPIO_CTRL[7:4] reflects levels on DIOx lines.

POWER MANAGEMENT

The SLP_CNT register (see Table 119) provides controls for

both power-down mode and sleep modes. The trade-off

between power-down mode and sleep mode is between idle

power and recovery time. Power-down mode offers the best

idle power consumption but requires the most time to recover.

Also, all volatile settings are lost during power-down but are

preserved during sleep mode.

For timed sleep mode, turn to Page 3 (DIN = 0x8003), write the

amount of sleep time to SLP_CNT[7:0] and then, set SLP_CNT[8]

= 1 (DIN = 0x9101) to start the sleep period. For a timed power-

down period, change the last command to set SLP_CNT[9] = 1

(DIN = 0x9102). To power down or sleep for an indefinite

period, set SLP_CNT[7:0] = 0x00 first, then set either

SLP_CNT[8] or SLP_CNT[9] to 1. Note that the command

takes effect when the CS line goes high. To awaken the device

from sleep or power-down mode, use one of the following

options to restore normal operation:

•

Assert CS from high to low.

•

Pulse RST low, then high again.

•

Cycle the power.

For example, set SLP_CNT[7:0] = 0x64 (DIN = 0x9064), then

set SLP_CNT[8] = 1 (DIN = 0x9101) to start a sleep period of

100 seconds.

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