There is no minimum speed specified for the I²C Bus. The bus can run as slow as the slave. The master can slow the clock to accommodate the slowest IC on the bus. With advancement in design, different modes of I²C were added to the I²C specification to support a variety of systems depending on the application. Using serial bi-directional data transfers that are 8-bit oriented, data can be sent at rates up to 100 Kbit/s in the Standard-mode, up to 400 Kbits/s in the Fast-mode, up to 1 Mbit/s in Fast-mode Plus (Fm+) or 3.4 Mbit/s in the High-speed mode. The Fast-mode Plus specification was defined to support I²C in systems requiring longer distances or many more slave devices. The unique value proposition of Fast-mode Plus is that it can support 10 times more loading on the bus. Hence, systems where the total device and trace capacitance would have exceeded 400 pF can now be supported. These new bus extension and control devices help expand the I²C bus beyond the 400 pF limit of about 20 devices and help control more devices, even those with the same address. The Fast-mode Plus I²C-bus can support up to 4000 pF of loading on the bus because of its higher drive strength (current sinking capability) which means more devices can be accommodated on the bus. These new devices are very popular with designers as they continue to expand and increase the range of use of I²C devices in maintenance and control applications.