The Si890x is available with three different port configurations. The Si8900 has a UART port that is specified to operate up to 234 kbps. This device also has an automatic baud rate detection algorithm built in to simplify the communications setup with any master controller. The Si8901 has an I²C interface and is specified to a 240 kbps data rate. With this configuration, a pull up resistor is necessary on the RSDA pin on the high-voltage side of the device. The SPI port is the fastest option with a 2.5 Mbps data rate and a 4-wire interface.