Z8FS040 Datasheet, PDF (29/56 Pages) Zilog, Inc. – ZMOTION Detection and Control Family Featuring Zilog’s PIR Technology

ZMOTION^TM Detection and Control Family
Product Specification
PIR Scan Rate (Bit 2)
PIR ADC conversion rate for the Pyroelectric Sensor
Controlled by application
The PIR engine performs the necessary ADC conversions on the PIR sensor input. Each conversion
generates an interrupt that is processed by the PIR engine from the EPIR_ADC_ISR macro. The PIR
Scan Rate bit determines the rate at which the ADC conversions are generated.
In Normal Scan Rate Mode (PIR Scan Rate set to 0), the Z8FS040 ADC peripheral is set to continuous
conversion mode which causes a conversion to be carried out automatically every 256 system clocks. In
this mode, the application is only required to execute the EPIR_ADC_ISR macro for each ADC interrupt.
The ADC continually runs and continuously generates interrupts.
When Low Scan Rate Mode is selected by setting this bit to a 1, continuous conversion mode is
disabled and the ADC is operated in single-shot mode such that each conversion takes 5129 system
clocks to complete. In this mode, the application S/W must initiate the ADC conversion request (set bit 7
of ADCCTL0) and execute the EPIR_ADC_ISR macro once every 5mS.
In Low Scan Rate Mode, the ADC is disabled between conversions to reduce power consumption.
Power consumption can be reduced further if the application S/W uses this mode in conjunction with the
CPU’s Halt or Stop modes. Alternately, this mode can be used to provide the application S/W with
additional CPU processing time.
Although the Low Scan Rate Mode provides the application with more processing power and the
opportunity for the system to reduce power consumption, the normal scan rate will provide better
sensitivity and range. While operating in Low Scan Rate Mode, sensitivity is reduced by approximately
20%. The performance of Direction Detection may also be reduced in this mode. EMC immunity is
disabled while in Low Scan Rate Mode.
If the PIR Scan Rate bit is changed during engine operation, the engine will stop detecting motion for up
to 200mS to avoid potential false motion detection. When changing the PIR Scan Rate mode, the
Advanced API registers must first be updated with the appropriate values.
0 = Normal Scan Rate Mode
1 = Low Scan Rate Mode
Dual Pyro Mode (Bit 0)
Dual Pyroelectric Sensor Signaling Mode
Controlled by Application
This bit determines if the PIR engine should accept signals from one or two pyroelectric sensors. When
configured for single pyro operation, only one sensor is used (connected to ANA2). When configured for
dual pyro operation, the engine will scan two sensors simultaneously. Dual pyro mode is typically used
to provide a larger area of coverage. The second pyroelectric sensor is connected to input ANA3. In
Dual Pyro Mode, motion on either sensor will generate a motion detected event.
0 = Single pyroelectric sensor mode
1 = Dual pyroelectric sensor mode
PS028506-1110
PRELIMINARY
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