pca8885 NXP Semiconductors, pca8885 Datasheet - Page 22

• Manufacturer Part Number: pca8885
• Description: Capacitive 8-channel Proximity Switch With Auto-calibration And Very Low Power Consumption
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA8885
Objective data sheet
13.8 Device cascading
When the transaction, after reading the SENS register, is not terminated with a STOP bit,
the PCA8885 repeatedly sends the content of SENS again. This provides a facility to
observe the sensor activity continuously. This transaction is illustrated in
Using two PCA8885 in a cascade (see
the other the secondary-chip. When the direct read transaction is executed in a cascaded
configuration, the primary-chip transmits its SENS content register immediately after the
address byte, followed by the secondary-chip transmitting its SENS register content.
If the transaction after reading the two SENS registers is not terminated with a STOP bit,
the primary-chip and the secondary-chip continue sending the content of the SENS
registers alternately. Such a transaction is illustrated in
It must be noted, that for this alternate data transfer only one PCA8885 has to be
addressed. By definition the primary-chip must be addressed (A0 bit in the address set to
logic 0). In this particular case, the secondary-chip reacts on the address of the
primary-chip. For all other transactions targeting the secondary-chip, it must be properly
addressed with A0 set to logic 1.
Two PCA8885 devices can be connected to the same I
8  8 keypads.
The device provides the following features to guarantee robust operation and to simplify
the system design using two devices:
Fig 14. Reading sensor data
Fig 15. Continuously reading sensor data
Fig 16. Reading sensor data, alternately from primary-chip and secondary-chip
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slave address
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slave address
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R/W
All information provided in this document is subject to legal disclaimers.
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server sensor data
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R/W
Rev. 1 — 24 November 2011
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Capacitive 8-channel proximity switch with auto-calibration
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sensor data
slave address
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client sensor data
Section
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A
0
R/W
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sensor data
13.8), one has to be the primary-chip and
sensor data
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server sensor data A
2
A
Figure
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C-bus, which facilitates up to
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sensor data
PCA8885
© NXP B.V. 2011. All rights reserved.
Figure
sensor data
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