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DESCRIPTION/ORDERING INFORMATION (CONTINUED)

PCA9539

WITH INTERRUPT OUTPUT, RESET, AND CONFIGURATION REGISTERS

SCPS130D – AUGUST 2005 – REVISED MARCH 2007

clock (SCL), serial data (SDA)].

The PCA9539 consists of two 8-bit Configuration (input or output selection), Input Port, Output Port, and Polarity

Inversion (active-high or active-low operation) registers. At power-on, the I/Os are configured as inputs. The

system master can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data

for each input or output is kept in the corresponding Input or Output register. The polarity of the Input Port

register can be inverted with the Polarity Inversion register. All registers can be read by the system master.

The system master can reset the PCA9539 in the event of a timeout or other improper operation by asserting a

state machine. Asserting RESET causes the same reset/initialization to occur without depowering the part.

The PCA9539 open-drain interrupt (INT) output is activated when any input state differs from its corresponding

Input Port register state and is used to indicate to the system master that an input state has changed.

INT can be connected to the interrupt input of a microcontroller. By sending an interrupt signal on this line, the

remote I/O can inform the microcontroller if there is incoming data on its ports without having to communicate via

The device outputs (latched) have high-current drive capability for directly driving LEDs. The device has low

current consumption.

The PCA9539 is identical to the PCA9555, except for the removal of the internal I/O pullup resistor, which

greatly reduces power consumption when the I/Os are held low, replacement of A2 with RESET, and a different

address range.

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