Z8FS021 datasheet(38/68 Pages) ZILOG

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PS028806-0315

Standard API Register Set

ZMOTION® Intrusion Detection

Product Specification

PIR Scan Rate (Bit 2)

PIR ADC conversion rate for the Pyroelectric Sensor; controlled by the 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 Z8FS021 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 isoperated in single-shot mode such that each conversion takes 5129 system

clocks to complete. In this mode, the application software 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 software uses this mode in conjunction

with the CPU’s Halt or Stop modes. Alternately, this mode can be used to provide the application

software 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 can also be reduced in this mode. EMC

immunity is disabled while in Low Scan Rate Mode.

• EMC immunity features, such as transient sensitivity and noise sensitivity, are disabled while in Low

Scan Rate Mode.

• If the PIR Scan Ratebit 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

2-Pulse Enable (Bit 1)

2-Pulse Detection Mode Enable; controlled by application

This bit determines if motion detection requires one or two motion pulses as the target passes across

the beams created by the Fresnel lens. With a Pulse Count of 1, a single motion pulse from the target

is required to qualify as valid motion. A Pulse Count of 2 requires two motion pulses from the target –

one positive and one negative – to qualify as valid motion. A Pulse Count of 2 is typically used in

harsher environmental conditions to decrease the chances of false triggers from sources such as fast

heating and cooling.

0 = One pulse of motion required for detection.

1 = Two pulses of motion required for detection.

Z8FS021 Datasheet(PDF) 38 Page - Zilog, Inc.

Z8FS021 Datasheet(HTML) 38 Page - Zilog, Inc.

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