ADIS16220

Rev. 0 | Page 12 of 20

CAPTURE MODE CONFIGURATION

The CAPT_CTRL register (see Table 15) offers three modes of

capture operation (manual, automatic, and event), along with a

number of configuration features for supporting these modes.

All three modes use the start/stop bit, located in GLOB_

CMD[11] (see Table 23) to manage the capture operation.

Table 15. CAPT_CTRL Bit Descriptions

Bit

Description (Default = 0x0020)

[15:7]

Reserved

[6]

Automatically store capture buffers to flash upon alarm

trigger (1 = enabled)

[5:4]

Pre-event capture length for event mode

00 = 64 samples

01 = 128 samples

10 = 256 samples

11 = 512 samples

[3:2]

Capture mode

00 = manual: use GLOB_CMD[11] to start capture

01 = automatic: use CAPT_PRD[9:0] to set capture period

10 = event: continuously monitor data for the conditions

set in ALM_CTRL, ALM_MAGA, ALM_MAG1, and ALM_MAG2.

11 = not used

[1]

Power-down between capture events

1 = enabled, which requires CS toggle to wake up

[0]

Reserved

Manual Capture Mode

The factory default configuration for capture mode is the manual

mode. In the manual mode, the ADIS16220 waits for a start

command to execute the capture event. Set GLOB_CMD[11] =

1 (DIN = 0xBF08) to start a capture in this mode. Once the

capture process begins, GLOB_CMD[11] resets to zero and

serves as a stop bit, until the capture event completes. Set

GLOB_CMD[11] = 1 to stop a capture event that is in progress.

Automatic Capture Mode

In the automatic mode, the ADIS16220 executes capture events

periodically, according to the time in CAPT_PRD (see Table 16).

Table 17 provides an example for configuring and starting the

automatic mode. When the device receives the start command,

it executes a capture event, and then starts the countdown for

executing the next capture event. Once the automatic mode

starts, GLOB_CMD[11] becomes a stop bit.

Table 16. CAPT_PRD Register Bit Descriptions

Bit

Description (Default = 0x0000)

[15:10]

Reserved

[9:8]

Scale

00 = 1 second/LSB

01 = 1 minute/LSB

10 = 1 hour/LSB

[7:0]

Data bits, binary format

Table 17. Example Automatic Mode Configuration Sequence

DIN

Description

0x9F02,

0x9E18

CAPT_PRD[15:8] = 0x02, set time scale to hours

CAPT_PRD[7:0] = 0x18, set the capture period to 24 hours

0x9C06

Set the device for trigger mode and enable shutdown

0xBF08

Start: device executes a capture and shuts down

Event Capture Mode

The event mode functions in a manner similar to a single-event

trigger on a digital oscilloscope. This mode is useful for captur-

ing shock events and for preshock motion/vibration analysis.

Once started, it monitors a continuous stream of real-time data for

a preset, event trigger condition. The event trigger settings are in

the following registers: ALM_CTRL (see Table 18), ALM_MAGA

(see Table 19), and ALM_MAG1/ALM_MAG2 (see Table 20).

When the acceleration or analog input signals trip the alarm

trigger settings, the device fills the capture buffers with pre-

trigger and post-trigger data, according to the pre-trigger

configuration in CAPT_CTRL[5:4].

Configuring the device in the event capture mode requires

four steps:

1.

Select which data channels to enable using ALM_CTRL.

2.

Set each threshold using the ALM_MAGx registers.

3.

Select event capture mode by setting CAPT_CTRL[3:2] = 10.

4.

Start the sampling by setting GLOB_CMD[11] = 1. Table 22

provides an example for configuring the device in this

mode. After the continuously sampling starts, setting

GLOB_CMD[11] = 1 stops the sampling process.

Table 18. ALM_CTRL Bit Descriptions

Bit

Description (Default = 0x0000)

[15:6]

Reserved

[5]

System alarm comparison polarity

1 = trigger when less than ALM_MAGS[11:0]

0 = trigger when greater than ALM_MAGS[11:0]

[4]

System alarm trigger source

1 = temperature, 0 = power supply

[3]

System alarm enable (ALM_MAGS)

1 = enabled, 0 = disabled

[2]

AIN2 alarm enable (ALM_MAG2)

1 = enabled, 0 = disabled

[1]

AIN1 alarm enable (ALM_MAG1)

1 = enabled, 0 = disabled

[0]

Acceleration alarm enable (ALM_MAGA)

1 = enabled, 0 = disabled

Table 19. ALM_MAGA Bit Descriptions

Bit

Description (Default = 0x0000)

[15:0]

Data bits for acceleration threshold setting;

twos complement, 19.073 mg/LSB.

Range = +8191 LSBs/−8192 LSBs

.