PCF8574P Remote 8-Bit I/O Expander for I2C Bus

This 8-bit input/output (I/O) expander for the two-line
bidirectional bus (I2C) is designed for 2.5V to 6V VCC
operation.
The PCF8574 device provides general-purpose
remote I/O expansion for most microcontroller families
by way of the I2C interface [serial clock (SCL), serial
data (SDA)].
The device features an 8-bit quasi-bidirectional I/O
port (P0–P7), including latched outputs with highcurrent drive capability for directly driving LEDs. Each
quasi-bidirectional I/O can be used as an input or
output without the use of a data-direction control
signal. At power on, the I/Os are high. In this mode,
only a current source to VCC is active.