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 viathe I2C interface.

The TCA9555RTWR 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 oroutputs by writing to the I/O configuration bits. The data for each input or output is kept in thecorresponding Input or Output register. The polarity of the Input Port register can be invertedwith the Polarity Inversion register.

The TCA9555RTWR is identical to the TCA9535, except for the inclusion of the internalI/O pull-up resistor, which pulls the I/O to a default high when configured as an input andundriven.

Three hardware pins (A0, A1, and A2) are used to program theI2C address, which allows up to eight TCA9555RTWR devices to share the sameI2C bus or SMBus. The fixed I2C address ofthe TCA9555RTWR is the same as the PCF8575,PCF8575C, andPCF8574, allowing up to eight of thesedevices in any combination to share the same I2C bus or SMBus.

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