The next device in is the SC18IS600/601. This an I2C controller with SPI interface. There are two devices in this Bridge. The SC18IS600 has an internal oscillator; therefore, no external clock is required. The SC18IS601 requires an external clock and it allows the device to run at faster SPI speed than the SC18IS600.This device is similar to the SC18IM700. It takes the commands and data from host, translate them to I2C electrical signals. It then sends them to I2C slave devices, which connect to its I2C bus. As you have already know, SPI is a four wire synchronous bus – data in, data out, clock, and chip select, the data is transferred on the transitions of the clock signal. The maximum SPI speed depends on which device you select. The SC16IS600 supports SPI speed up to 1Mbps, and the SC16IS601 can run as fast as 3Mbps. Both devices offer I2C speed up to 400Kbps. Each of these device has internal FIFO to buffer the transmit and receive data. The FIFO size is 96 byte each; therefore, the command an data message from host can be as long as 96 bytes. Unlike the SC18IM700, these two device support interrupt mechanism to communicate with the host. When the transmit FIFO is empty or when the receive FIFO is filled with data, these two devices will interrupt the host. Beside the I2C master function, these two devices also provide users with up to 5 GPIO pins. These pins can be set up as input, output, quasi bi-directional, or open-drain output. All the GPIO pins are 5V tolerant. These devices also support power down mode to reduce current consumption to less than 10uA. The devices can be put to this mode by sending it a command. Toggling WAKEUP pin will power the part back up.