ADIS16448SLASHPCBZ datasheet(21/24 Pages) AD

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Data Sheet

ADIS16448

Rev. B | Page 21 of 24

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[15:8]) with the values in the ALM_MAGx registers

listed in Table 49 and Table 50, using ALM_MAGx[15] to deter-

mine the trigger polarity. The data format in these registers

matches the format of the data selection in ALM_CTRL[15:8].

See Table 54, Alarm 1, for a static alarm configuration example.

Table 49. ALM_MAG1 (Base Address = 0x40), Read/Write

Bits

Description (Default = 0x0000)

[15:0]

Threshold setting; matches for format of

ALM_CTRL[11:8] output register selection

Table 50. ALM_MAG2 (Base Address = 0x42), Read/Write

Bits

Description (Default = 0x0000)

[15:0]

Threshold setting; matches for format of

ALM_CTRL[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, located in Table 51. See Table 54, Alarm 2,

for a dynamic alarm configuration example.

Table 51. 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 52. 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

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

alarm condition. The ALM_CTRL[2:0] bits provide controls

for a hardware indicator using DIO1 or DIO2.

Table 53. 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 = XMAGN_OUT

1001 = YMAGN_OUT

1010 = ZMAGN_OUT

1011 = BARO_OUT

1100 = TEMP_OUT

[11:8]

Alarm 1 data source selection (same as Alarm 2)

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

Alarm 1, dynamic/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 54 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 54. Alarm Configuration Example

DIN

Description

0xCD36,

ALM_CTRL = 0x36AF

0xCCAF

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

0xC704,

0xC6E2

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

0xC503,

0xC448

ALM_MAG1 = 0x0348 = 840 LSB = +0.7 g

0xC866

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

82 samples ÷ 819.2 SPS = ~100 ms

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