Z8FS040 datasheet(36/56 Pages) ZILOG

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ZMOTION

TM Detection and Control Family

Product Specification

PS028506-1110

PRELIMINARY

PIR Advanced Status/Control Register 2 (ePIR_ASC2)

Bit

Field

Lock level

Window Size

Window Update Rate

Control

R/W

Address

F2H

Lock Level (Bits 5-7)

Controlled by application

This parameter sets the minimum slope change in the signal that can be considered valid motion. This

prevents small signal changes caused by environmental or Vcc shifts from causing a false detection.

Use this value in combination with PIR Sensitivity and Range Control settings to balance sensitivity and

stability to the particular lens and pyroelectric sensor being used.



Smaller values allow subtle signals with lower slopes to be considered motion events at the

expense of potential false motion events.



Larger values allow the system to ignore smaller signal slope changes at the expense of

potentially missing smaller motion events.

Window Size (Bits 3-4)

Controlled by application

This register determines the size of the control limit window. A larger window size produces more stable

control limits at the cost of additional CPU usage. If a smaller window size is used, the more frequently

the window can be calculated which allows it to track the signal better.

00 – Reserved

01 – Small window

02 – Medium window

03 – Large window

Window Update Rate (Bits 0-2)

Controlled by application

This register determines how frequently the control limits are calculated. It is measured in PIR samples.

A smaller number produces more frequent calculations which allow the control limits to track the signal

better, at the cost of increased CPU usage. The valid range is 0 to 7.

The window is updated every 4 + (Window Update Rate * 2) PIR samples.

Z8FS040 Datasheet(PDF) 36 Page - Zilog, Inc.

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