This 16-bit I/O expander for the two-line bidirectional bus (I2C) is designed for 2.3-V to 5.5-V VCC operation. It provides general-purpose remote I/O expansion for most microcontroller families via the I2C interface [serial clock (SCL), serial data (SDA)].

The PCA9539DBQR 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 PCA9539DBQR in the event of a time-out or other improper operation by asserting a low in the RESET, and a different address range.

Two hardware pins (A0 and A1) are used to program and vary the fixed I2C address and allow up to four devices to share the same I2C bus or SMBus.

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