ADIS1644XSLASHFLEX datasheet(20/23 Pages) AD

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ADIS16446

Data Sheet

Rev. 0 | Page 20 of 23

ALARMS

Alarm 1 and Alarm 2 provide two independent alarms with

programmable levels, polarity, and data sources.

STATIC ALARM USE

The static alarms setting compares the data source selection

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

registers listed in Table 36 and Table 37, using ALM_MAGx,

Bits 15, to determine the trigger polarity. The data format in

these registers matches the format of the data selection in

ALM_CTRL, Bits[15:8]. See Table 41, Alarm 1, for a static

alarm configuration example.

Table 36. ALM_MAG1 (Base Address = 0x40), Read/Write

Bits

Description (Default = 0x0000)

[15:0]

Threshold setting, matches the format of the

ALM_CTRL, Bits[11:8] output register selection

Table 37. ALM_MAG2 (Base Address = 0x42), Read/Write

Bits

Description (Default = 0x0000)

[15:0]

Threshold setting, matches the format of the

ALM_CTRL, Bits[15:12] output register selection

DYNAMIC ALARM USE

The dynamic alarm setting monitors the data selection for a

rate of change comparison. The rate of change comparison is

represented by the magnitude in the ALM_MAGx registers

over the time represented by the number of samples setting in

the ALM_SMPLx registers (see Table 38 and Table 39). See

Table 41, Alarm 2, for a dynamic alarm configuration example.

Table 38. ALM_SMPL1 (Base Address = 0x44), Read/Write

Bits

Description (Default = 0x0000)

[15:8]

Not used

[7:0]

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

Table 39. ALM_SMPL2 (Base Address = 0x46), Read/Write

Bits

Description (Default = 0x0000)

[15:8]

Not used

[7:0]

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

ALARM REPORTING

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

alarm condition. Bits[2:0] of ALM_CTRL provide controls for a

hardware indicator using DIO1 or DIO2.

Table 40. ALM_CTRL (Base Address = 0x48), Read/Write

Bits

Description (Default = 0x0000)

[15:12]

Alarm 2 data source selection

0000 = disable

0001 = XGYRO_OUT

0010 = YGYRO_OUT

0011 = ZGYRO_OUT

0100 = XACCL_OUT

0101 = YACCL_OUT

0110 = ZACCL_OUT

0111 = unused

1001 = unused

1010 = unused

1011 = unused

1100 = TEMP_OUT

[11:8]

Alarm 1 data source selection (same as Alarm 2)

Alarm 2, dynamic or static (1 = dynamic, 0 = static)

Alarm 1, dynamic or static (1 = dynamic, 0 = static)

Alarm 2, polarity (1 = greater than ALM_MAG2)

Alarm 1, polarity (1 = greater than ALM_MAG1)

Data source filtering (1 = filtered, 0 = unfiltered)

Alarm indicator (1 = enabled, 0 = disabled)

Alarm indicator active polarity (1 = high, 0 = low)

Alarm output line select (1 = DIO2, 0 = DIO1)

Alarm Example

Table 41 offers an example that configures Alarm 1 to trigger

when filtered ZACCL_OUT data drops below 0.7 g and Alarm 2

to trigger when filtered ZGYRO_OUT data changes by more

than 50°/sec over a 100 ms period, or 500°/sec2. The filter

setting helps reduce false triggers from noise and refines the

accuracy of the trigger points. The ALM_SMPL2 setting of

82 samples provides a comparison period that is approximately

equal to 100 ms for an internal sample rate of 819.2 SPS.

Table 41. Alarm Configuration Example

DIN

Description

0xC936, 0xC8AF

ALM_CTRL = 0x36AF

Alarm 2: dynamic, Δ-ZGYRO_OUT (Δ-time,

ALM_SMPL2) > ALM_MAG2

Alarm 1: static, ZACCL_OUT < ALM_MAG1,

filtered data DIO2 output indicator, positive

polarity

0xC313, 0xC288

ALM_MAG2 = 0x04E2 = 1,250 LSB = 50°/sec

0xC10A, 0xC0F0

ALM_MAG1 = 0x0348 = 840 LSB = +0.7 g

0xC652

ALM_SMPL2, Bits[7:0] = 0x52 = 82 samples,

82 samples ÷ 819.2 SPS = ~100 ms

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