8.5.1.3 I²C Speed Modes

The I²C bus operates at one of three speeds. Standard mode allows a clock frequency of up to 100 kHz; fast mode permits a clock frequency of up to 400 kHz; and high-speed mode (also called Hs mode) allows a clock frequency of up to 3.4 MHz. The ADS101x are fully compatible with all three modes.

No special action is required to use the ADS101x in standard or fast mode, but high-speed mode must be activated. To activate high-speed mode, send a special address byte of 00001xxx following the START condition, where xxx are bits unique to the Hs-capable master. This byte is called the Hs master code, and is different from normal address bytes; the eighth bit does not indicate read/write status. The ADS101x do not acknowledge this byte; the I²C specification prohibits acknowledgment of the Hs master code. Upon receiving a master code, the ADS101x switch on Hs mode filters, and communicate at up to 3.4 MHz. The ADS101x switch out of Hs mode with the next STOP condition.

For more information on high-speed mode, consult the I²C specification.