ALTERA推荐状态机编码方式.pdf

Application Brief 131 State Machine Encoding State Machine Encoding May 1994, ver. 1 Application Brief 131 Summary Each state of a state machine can be represented with a unique pattern of high (1) and low (0) register output signals, a process called “encoding.” The two primary encoding methods are binary and one-hot encoding. This application brief describes both methods and discusses how to select the encoding scheme that best suits your design, so that you can ensure efficient performance and resource usage. Binary The relationship between the number of state bits (B) and number of states (S) in a binary-encoded state machine is represented by the following Encoding equation: B = log2 (S) With this formula, you can easily determine the minimum number of state bits required for a binary-encoded state machine. For example, to implement a 4-state state machine with a binary encoding scheme, you can use two flipflops (i.e., state bits) to uniquely define the four states as follows: state1 = 00 state2 = 01 state3 = 10 state4 = 11 This example implements the state machine with a left-to-right sequential binary encoding. You can also use a Gray co