The PCF8574T/3,518 can support I2C bus frequencies up to 400 kHz.
The reset pin (RST) is an active-low input that resets the device when pulled low. It's recommended to tie the RST pin to VCC through a 1 kΩ resistor to ensure proper operation.
The PCF8574T/3,518 can sink or source up to 25 mA of current on its I/O pins.
The PCF8574T/3,518 has a register-based configuration. You need to write to the configuration register (address 0x00) to set the I/O pins as input or output. A '1' in the register sets the pin as an input, while a '0' sets it as an output.
The internal pull-up resistors on the I/O pins of the PCF8574T/3,518 are used to pull the pins high when they are configured as inputs. This helps to prevent floating inputs and ensures proper operation.
PCF8574T/3,518 datasheet
by NXP Semiconductors
