Datasheet
PCA9672 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 3 — 27 May 2013 16 of 36
NXP Semiconductors
PCA9672
Remote 8-bit I/O expander for Fm+ I
2
C-bus with interrupt and reset
10. Application design-in information
10.1 Bidirectional I/O expander applications
In the 8-bit I/O expander application shown in Figure 20, P0 and P1 are inputs, and P2 to
P7 are outputs. When used in this configuration, during a write, the input (P0 and P1)
must be written as HIGH so the external devices fully control the input ports. The
desired HIGH or LOW logic levels may be written to the I/Os used as outputs (P2 to P7).
If 10 A internal output HIGH is not enough current source, the port needs external pull-up
resistor. During a read, the logic levels of the external devices driving the input ports (P0
and P1) and the previous written logic level to the output ports (P2 to P7) will be read.
The GPIO also has an interrupt line (INT
) that can be connected to the interrupt logic of
the microprocessor. By sending an interrupt signal on this line, the remote I/O informs the
microprocessor that there has been a change of data on its ports without having to
communicate via the I
2
C-bus.
The GPIO also has a reset line (RESET
) that can be connected to an output pin of the
microcontroller.
10.2 How to read and write to I/O expander (example)
In the application example of PCA9672 shown in Figure 20, the microcontroller wants to
control the P3 switch ON and the P7 LED ON when the temperature sensor P0 changes.
1. When the system power on:
Core Processor needs to issue an initial command to set P0 and P1 as inputs and
P[7:2] as outputs with value 1010 00 (LED off, MP3 off, camera on, audio off,
switch off and latch off).
2. Operation:
When the temperature changes above the threshold, the temperature sensor signal
will toggle from HIGH to LOW. The INT
will be activated and notifies the ‘core
processor’, that there have been changes on the input pins. Read the input register.
If P0 = 0 (temperature sensor has changed), then turn on LED and turn on switch.
Fig 20. Bidirectional I/O expander application
002aac330
V
DD
temperature sensor
battery status
control for latch
control for switch
control for audio
control for camera
control for MP3
P0
P1
P2
P3
P4
P5
P6
P7
V
DD
SDA
SCL
INT
AD0
AD1
CORE
PROCESSOR
V
DD
RESET