Z8FS040 Datasheet, PDF (36/56 Pages) Zilog, Inc. – ZMOTION Detection and Control Family Featuring Zilog’s PIR Technology

ZMOTION^TM Detection and Control Family
Product Specification
PIR Advanced Status/Control Register 2 (ePIR_ASC2)
Bit
7
6
5
4
3
Field
Control
Address
Lock level
R/W
Window Size
R/W
F2H
2
1
0
Window Update Rate
R/W
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.
PS028506-1110
PRELIMINARY
31