ADIS16136

Data Sheet

Rev. A | Page 14 of 20

ALARMS

The alarm function provides monitoring for two independent

conditions. Table 22 contains a list of registers that provide

configuration and control inputs for the alarm function.

Table 22. Registers for Alarm Configuration

Register

Address

Description

ALM_MAG1

0x10

Alarm 1, trigger setting

ALM_MAG2

0x12

Alarm 2, trigger setting

ALM_SMPL1

0x14

Alarm 1, sample period

ALM_SMPL2

0x16

Alarm 2, sample period

ALM_CTRL

0x18

Alarm configuration

The ALM_CTRL register (see Table 26) provides data source

selection (Bits[15:8]), static/dynamic setting for each alarm

(Bits[7:6]), trigger polarity (Bits[5:4]), data source filtering

(Bit 3), and an alarm indicator signal (Bits[2:0]).

STATIC ALARM USE

The static alarms setting compares the data source selection

(ALM_CTRL[15:8]) with the values in the ALM_MAGx

registers in Table 23 and Table 24. The data format in these

registers matches the format of the data selection in

ALM_CTRL[15:8]. ALM_CTRL[5:4] provide polarity

settings. See Table 27 for a static alarm configuration

example.

Table 23. ALM_MAG1 Bit Descriptions

Bits

Description (Default = 0x0000)

[15:0]

Threshold setting; matches format of the

ALM_CTRL[11:8] selection

Table 24. ALM_MAG2 Bit Descriptions

Bits

Description (Default = 0x0000)

[15:0]

Threshold setting; matches for format of the

ALM_CTRL[15:12] selection

DYNAMIC ALARM USE

The dynamic alarm setting monitors the data selection for a

rate-of-change comparison. The rate of change is represented

by the magnitude in the ALM_MAGx registers over the time

represented by the number of samples in the ALM_SMPLx

register (see Table 25). See Table 27 for a dynamic alarm

configuration example.

Table 25. ALM_SMPL1, ALM_SMPL2 Bit Descriptions

Bits

Description (Default = 0x0000)

[15:8]

Not used

[7:0]

Binary, number of samples (both 0x00 and 0x01 = 1)

ALARM REPORTING

DIAG_STAT[9:8] provide error flags that indicate an alarm

condition. ALM_CTRL[2:0] provide controls for a hardware

indicator using DIO1 or DIO2.

Table 26. ALM_CTRL Bit Descriptions

Bits

Description (Default = 0x0000)

[15:12]

Alarm 2 source selection

0000 = disable

0001 = GYRO_OUT (does not include GYRO_OUT2)

0010 = TEMP_OUT

0011 = DIAG_STAT

[11:8]

Alarm 1 source selection (same as Alarm 2)

7

Rate-of-change enable for Alarm 2

(1 = rate of change, 0 = static level)

6

Rate-of-change enable for Alarm 1

(1 = rate of change, 0 = static level)

5

Comparison polarity for Alarm 2

(1 specifies >ALM_MAG2, 0 specifies <ALM_MAG2)

4

Comparison polarity for Alarm 1

(1 specifies >ALM_MAG1, 0 specifies <ALM_MAG1)

3

Comparison data filter setting1

(1 = Bartlett filter, 0 = no filtering)

2

Alarm output enable

(1 = enabled, 0 = disabled)

1

Alarm output polarity

(1 = active high, 0 = active low)

0

Alarm output line select

(1 = DIO2, 0 = DIO1)

1

Filtering applies to GYRO_OUT only.

Alarm Example

Table 27 offers an example that configures Alarm 1 to trigger

when filtered GYRO_OUT data drops below 50°/sec and Alarm 2

to trigger when filtered GYRO_OUT data changes by more

setting helps reduce false triggers from noise and refine the

accuracy of the trigger points. The ALM_SMPL2 setting of

102 samples provides a comparison period that is 99.6 ms for

an internal sample rate of 1024 SPS. There is no need to pro-

gram ALM_SMPL1 because Alarm 1 is a static alarm in this

example.

Table 27. Alarm Configuration Example 1

DIN

Description

0x9911,

0x98AF

ALM_CTRL = 0x11AF

Alarm 2: dynamic; ΔGYRO_OUT

(Δtime, ALM_ SMPL2) > ALM_MAG2

Alarm 1: static; GYRO_OUT < ALM_MAG1

use filtered data source for comparison

DIO2 output indicator, positive polarity

0x930A,

0x92AF

ALM_MAG2 = 0x0AAF, (+50°/sec)

0x910A,

0x90AF

ALM_MAG1 = 0x0AAF, (+50°/sec)

0x9666

ALM_SMPL2[7:0] = 0x66, (102 samples)