Datasheet

PCA9671 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Product data sheet Rev. 3 — 29 September 2011 18 of 33
NXP Semiconductors
PCA9671
Remote 16-bit I/O expander for Fm+ I
2
C-bus with reset
10. Application design-in information
10.1 Bidirectional I/O expander applications
In the 8-bit I/O expander application shown in Figure 21, P00 and P01 are inputs, and P02
to P07 are outputs. When used in this configuration, during a write, the input (P00 and
P01) 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 (P02 to
P07). During a read, the logic levels of the external devices driving the input ports (P00
and P01) and the previous written logic level to the output ports (P02 to P07) will be read.
The GPIO also has a reset line (RESET
) that can be connected to an output pin of the
microprocessor. Since the device does not have an interrupt output, changes of the I/Os
can be monitored by reading the input registers. If both a RESET
and INT are needed,
use the PCA9673.
Fig 20. Acknowledgement on the I
2
C-bus
002aaa987
S
START
condition
9821
clock pulse for
acknowledgement
not acknowledge
acknowledge
data output
by transmitter
data output
by receiver
SCL from master
Fig 21. Bidirectional I/O expander application
002aac253
V
DD
temperature sensor
battery status
control for latch
control for switch
control for audio
control for camera
control for MP3
P00
P01
P02
P03
P04
P05
P06
P07
V
DD
SDA
SCL
RESET
A0
A1
A2
CORE
PROCESSOR
V
DD