What are differences between one hot and binary encoding?

Common classifications used to explain the state encoding of an FSM is Binary or highly encoded and one hot.

A binary-encoded FSM design only needs as several flip-flops as are required to uniquely encode the number of states into the state machine. The actual no. of flip-flops needed is equal to the ceiling of the log-base-two of the number of states into the FSM.

A one hot FSM design needs a flip-flop for each state into the design and only one flip-flop that means there flip-flop representing the current or "hot" state, is set at a time into a one hot FSM design. For a condition machine with 9 to 16 states, the binary FSM simply needs 4 flip-flops but a one hot FSM needs a flip-flop for each state into the design.

FPGA vendors often recommend by using a one hot state encoding style since flip-flops are plentiful into an FPGA and the combinational logic needed to implement a one hot FSM design is typically smaller than most binary encoding styles. As FPGA performance is usually associated to the combinational logic size of the FPGA design, one hot FSMs usually run faster than a binary encoded FSM along with larger combinational logic blocks.