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 13 of 36
NXP Semiconductors
PCA9672
Remote 8-bit I/O expander for Fm+ I
2
C-bus with interrupt and reset
8.5 Interrupt output (INT)
The PCA9672 provides an open-drain output (INT) which can be fed to a corresponding
input of the microcontroller (see Figure 15
). As soon as a port input is changed, the INT
will be active (LOW) and notify the microcontroller.
An interrupt is generated at any rising or falling edge of the port inputs. After time t
v(Q)
, the
signal INT
is valid.
The interrupt will reset to HIGH when data on the port is changed to the original setting or
data is read or written by the master.
In the Write mode, the interrupt may be reset (HIGH) on the rising edge of the
acknowledge bit of the data byte and also on the rising edge of the write to port pulse. The
interrupt will always be reset (HIGH) on the falling edge of the write to port pulse (see
Figure 13
).
The interrupt is reset (HIGH) in the rising edge of the read from port pulse (see Figure 14
).
During the interrupt reset, any I/O change close to the read or write pulse may not
generate an interrupt, or the interrupt will have a very short pulse. After the interrupt is
reset, any change in I/Os will be detected and transmitted as an INT
.
At power-on reset all ports are in Input mode and the initial state of the ports is HIGH,
therefore, for any port pin that is pulled LOW or driven LOW by external source, the
interrupt output will be active (output LOW).
8.6 RESET input
A reset can be accomplished by holding the RESET pin LOW for a minimum of t
w(rst)
. The
PCA9672 registers and I
2
C-bus state machine will be held in their default state until the
RESET
input is once again HIGH. The RESET input pin requires a pull-up resistor to V
DD
if no active connection is used.
Fig 15. Application of multiple PCA9672s with interrupt
002aac328
V
DD
MICROCOMPUTER
INT
PCA9672
INT
PCA9672
INT
device 1 device 2
PCA9672
INT
device 8