ZDP323B Series Digital PIR Sensor

Product Specification

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PS041703-0324 - Preliminary

Page 8

9.4.1 Reading Peak Hold Data

The ZDP323B Digital PIR Sensor tracks the peak value from the output of the bandpass

filter which can be read over the I2C interface. This value is provided in a 12-

bit, signed, 2’s

compliment format.

The peak hold value is tracked each time the bandpass filter output is updated. The output

value from the bandpass filter is compared against the current peak hold value. If the

absolute value of the bandpass filter output is greater than the current peak hold absolute

value, it is saved as the new peak hold value.

Figure 11 shows the I2C transaction used to read the Peak Hold Data using the 7-bit

General Call transaction and Figure 12 shows the I2C transaction required to read the Peak

Hold Data using a 10-bit address.

SDA (Pin 1)

SCL (Pin 3) Start

0

0

0

0

0

SA6 SA5 SA4 SA3 SA2 SA1 SA0

0

0

Slave Address (7-bit)

ACK

X

X

X

X

D11 D10 D9

Peak Hold Data (Upper 8-bit)

D8 ACK

Stop

R

D7

D6

D5

D4

D3

D2

D1

Peak Hold Data (Lower 8-bit)

D0

ACK

Peak Hold Data (12-bit)

Figure 11 - Peak Hold Data Read (7-bit Address)

SDA (Pin 1)

SCL (Pin 3)

SDA (Pin 1)

SCL (Pin 3)

Start

1

1

1

1

0

1

1

1

1

0

SA9 SA8

1

1

Slave Address (Upper 2-bit)

W ACK

0

0

0

0

0

SA7 SA6 SA5 SA4 SA3 SA2 SA1

X

X

Slave Address (Lower 8-bit)

SA0

X

Stop

1

1

1

1

0

1

1

1

1

0

SA9 SA8

1

1

Slave Address (Upper 2-bit)

R

ACK

Repeated Start

X

X

X

X

D11 D10 D9

Peak Hold Data (Upper 8-bit)

D8 ACK D7 D6

D5

D4

D3

D2

D1

Peak Hold Data (12-bit)

D0 ACK

Figure 12 - Peak Hold Data (10-bit Address)

When the Peak Hold value is read, it is reset to 0 and tracking starts over. If the Peak Hold

Data is read at a rate shorter than TCYC, the value returned could be 0 (since it has not been

updated since the last read). Therefore, it is recommended to read the Peak Hold data at a

rate not less than ~10ms.

The Peak Hold value should not be read until the sensor stability time (TSTAB) has

completed.