This 16-bit I/O expander for the two-line bidirectional bus (I2C) is designed for 1.65-V to 5.5-V VCCoperation. It provides general-purpose remote I/O expansion for most microcontroller families via the I2C interface.

The TCA9555 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.

The TCA9555 is identical to theTCA9535, except for the inclusion of the internal I/O pull-up resistor, which pulls the I/O to a default high when configured as an input and undriven.Read more