TEXAS INSTRUMENTS PCF8574AN

This 8 bit input/output expander for the two line bidirectional bus (I2C) is designed for 2.5V to 6V VCC operation. The PCF8574AN provides general purpose remote I/O expansion for most microcontroller families via 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 high current 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. An additional strong pull-up to VCC allows fast rising edges into heavily loaded outputs. This device turns on when an output is written high and is switched off by the negative edge of SCL. The I/Os should be high before being used as inputs.