ADIS16133

Rev. 0 | Page 13 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]), rate-of-change enable (Bits[7:6]), trigger

polarity (Bits[5:4]), data source filtering (Bit 3), and an alarm

indicator signal (Bits[2:0]).

Static Alarm Use

Set the rate-of-change bits (ALM_CTRL[7:6]) equal to zero

for static alarm use, which 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]

Trigger setting; matches format of the ALM_CTRL[11:8]

selection

Table 24. ALM_MAG2 Bit Descriptions

Bits

Description (Default = 0x0000)

[15:0]

Trigger setting; matches format of the ALM_CTRL[15:12]

selection

Dynamic Alarm Use

Set the rate-of-change bits (ALM_CTRL[7:6]) equal to 1 to enable

the dynamic alarm mode, which 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 setting in the ALM_SMPLx

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

tion 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 data source selection

0000 = disable

0001 = GYRO_OUT (does not include GYRO_OUT2)

0010 = TEMP_OUT

0011 = DIAG_STAT

[11:8]

Alarm 1 data source selection (same as Alarm 2)

[7]

Rate-of-change enable for Alarm 2

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

[6]

Rate-of-change enable for Alarm 1

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

[5]

Trigger polarity for Alarm 2

(1 specifies >ALM_MAG2, 0 specifies <ALM_MAG2)

[4]

Trigger 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)

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 program

ALM_SMPL1 because Alarm 1 is a static alarm in this example.

Table 27. Alarm Configuration Example 1

DIN

Description

0x9911

ALM_CTRL = 0x11AF

0x98AF

Alarm 2: dynamic; Δ-GYRO_OUT

(Δ-time, ALM_ SMPL2) > ALM_MAG2

Alarm 1: static; GYRO_OUT < ALM_MAG1

Set alarms to track filtered data

DIO2 = output indicator, positive polarity

0x930F

ALM_MAG2 = 0x0FA0, (200°/sec)

0x92A0

0x910F

ALM_MAG1 = 0x0FA0, (200°/sec)

0x90A0

0x9666

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