CAT9555

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7

INT: Interrupt Output

The open−drain interrupt output is activated when one of

the port pins configured as an input changes state (differs

from the corresponding input port register bit state). The

interrupt is deactivated when the input returns to its previous

state or the input port register is read.

Since there are two 8−bit ports that are read independently,

the interrupt caused by Port 0 will not be cleared by a read

of Port 1, or vice versa.

Changing an I/O from an output to an input may cause a

false interrupt if the state of the pin does not match the

contents of the input port register.

Output Port

Register Data

Input Port

Register Data

Polarity

Register Data

Polarity

Inversion Register

Write

Polarity

Register

Data from

Shift Register

Read Pulse

Write Pulse

Write

Configuration

Data from

Shift Register

Data from

Shift Register

Configuration

Register

D

Q

FF

D

Q

FF

D

Q

LATCH

D

Q

FF

Q1

Q2

Output Port

Register

Input Port

Register

Figure 6. Simplified Schematic of I/Os

Pulse

Q

Q

Q

Q

To INT

I/O Pin

100 kW