PCA9675DB datasheet(16/34 Pages) PHILIPS

16 / 34 page

PCA9675_1

Product data sheet

Rev. 01 — 1 February 2007

16 of 34

NXP Semiconductors

PCA9675

Remote 16-bit I/O expander for Fm+ I2C-bus with interrupt

8.4 Power-on reset

When power is applied to VDD, an internal Power-On Reset (POR) holds the PCA9675 in

a reset condition until VDD has reached VPOR. At that point, the reset condition is released

and the PCA9675 registers and I2C-bus/SMBus state machine will initialize to their default

states. Thereafter VDD must be lowered below 0.2 V to reset the device.

8.5 Interrupt output (INT)

The PCA9675 provides an open-drain interrupt (INT) which can be fed to a corresponding

input of the microcontroller (see Figure 17, Figure 18, and Figure 19). This gives these

chips a kind of master function which can initiate an action elsewhere in the system.

An interrupt is generated by any rising or falling edge of the port inputs. After time t(v)D the

signal INT is valid.

The interrupt disappears when data on the port is changed to the original setting or data is

read from or written to the device which has generated the interrupt.

In the write mode, the interrupt may become deactivated (HIGH) on the rising edge of the

write to port pulse. On the falling edge of the write to port pulse the interrupt is deﬁnitely

deactivated (HIGH).

The interrupt is reset in the read mode on the rising edge of the read from port pulse.

During the resetting of the interrupt itself, any changes on the I/Os may not generate an

interrupt. After the interrupt is reset any change in I/Os will be detected and transmitted as

an INT.

Fig 19. Application of multiple PCA9675s with interrupt

002aab635

VDD

MICROCOMPUTER

INT

PCA9675

INT

PCA9675

INT

device 1

device 2

PCA9675

INT

device 8

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