Overview

Product details

    The 8574TM provides universal remote I/O expansion via a two-wire bidirectional I²C bus (Serial Clock (SCL), Serial Data (SDA)). The device consists of eight quasi-bidirectional ports, 100 kHz I²C bus interfaces, three hardware address inputs, and interrupt outputs operating between 2.5 V and 6 V. Quasi-bidirectional ports can be assigned independently as inputs for monitoring interruption states or keyboards, or as outputs for activation indicator devices such as leds. The system host can read or write from the input port to the output port via a single register. The low current consumption of 2.5μA(typical static) is ideal for mobile applications and for direct drive leds with latched output ports. The 8574TM is identical except for different fixed parts from the device address. Three hardware address pins allow 8 of each device to be on the same I²C bus, so you can have up to 16 of these I/O extenders 8574TM on the same I²C bus, supporting up to 128 I/ OS (for example, 128 leds). The active LOW open interrupt output (INT) can be connected to the microcontroller's interrupt logic and activated when any input state is different from its corresponding input port register state. It is used to indicate to the microcontroller that the input state has changed and that the device needs to interrogate the input registers without the microcontroller continuously polling them through the I²C bus. Internal Power-On Reset (POR) initializes I/O to an input with a weak internal pull-up 100μA current source.