HDLBits-Fsm3onehot

The following is the state transition table for a Moore state machine with one input, one output, and four states. Use the following one-hot state encoding: A=4'b0001, B=4'b0010, C=4'b0100, D=4'b1000.

Derive state transition and output logic equations by inspection assuming a one-hot encoding. Implement only the state transition logic and output logic (the combinational logic portion) for this state machine. (The testbench will test with non-one hot inputs to make sure you're not trying to do something more complicated).

| State | Next state || Output |

State in=0 in=1 Output
A A B 0
B C B 0
C A D 0
D C B 1
What does "derive equations by inspection" mean?

One-hot state machine encoding guarantees that exactly one state bit is 1. This means that it is possible to determine whether the state machine is in a particular state by examining only one state bit, not all state bits. This leads to simple logic equations for the state transitions by examining the incoming edges for each state in the state transition diagram.

For example, in the above state machine, how can the state machine can reach state A? It must use one of the two incoming edges: "Currently in state A and in=0" or "Currently in state C and in = 0". Due to the one-hot encoding, the logic equation to test for "currently in state A" is simply the state bit for state A. This leads to the final logic equation for the next state of state bit A: next_state[0] = state[0]&(~in) | state[2]&(~in). The one-hot encoding guarantees that at most one clause (product term) will be "active" at a time, so the clauses can just be ORed together.

When an exercise asks for state transition equations "by inspection", use this particular method. The judge will test with non-one-hot inputs to ensure your logic equations follow this method, rather that doing something else (such as resetting the FSM) for illegal (non-one-hot) combinations of the state bits.

Although knowing this algorithm isn't necessary for RTL-level design (the logic synthesizer handles this), it is illustrative of why one-hot FSMs often have simpler logic (at the expense of more state bit storage), and this topic frequently shows up on exams in digital logic courses.

Module Declaration

复制代码
module top_module(
    input in,
    input [3:0] state,
    output [3:0] next_state,
    output out); 

独热编码:使用每一位表示一个状态, 例如 有A、B、C、D四个状态,则采用state【4:0】

A为4'b0001 B为4'b0010 C为4'b0100 D为4'b1000

则可以设置 parameter A = 0,

B = 1,

C = 2,

D = 3

通过state[A]是否为1就可以判断当前状态是否为A,同理通过state【B】是否为1就可以判断当前状态是否为B。

以下为该题代码:

cpp 复制代码
module top_module(
    input in,
    input [3:0] state,
    output [3:0] next_state,
    output out); 

    parameter A = 0, // 独热编码第0位为1表示A
              B = 1, // 独热编码第0位为1表示B
              C=  2, 
              D=  3;

    // State transition logic: Derive an equation for each state flip-flop.
    assign next_state[A] = state[0]&(~in) | state[2]&(~in);
    assign next_state[B] = state[0]&in | state[1]&in | state[3]∈
    assign next_state[C] = state[1]&(~in) | state[3]&(~in);
    assign next_state[D] = state[2]∈

    // Output logic: 
    assign out = state[D];

endmodule
相关推荐
禾川兴 132424006883 小时前
国产芯片解析:龙讯HDMI Splitter系列:多屏共享高清
单片机·fpga开发·适配器模式
威视锐科技7 小时前
软件定义无线电36
网络·网络协议·算法·fpga开发·架构·信息与通信
JINX的诅咒7 小时前
CORDIC算法:三角函数的硬件加速革命——从数学原理到FPGA实现的超高效计算方案
算法·数学建模·fpga开发·架构·信号处理·硬件加速器
云山工作室11 小时前
基于FPGA的智能垃圾分类装置(论文+源码)
单片机·fpga开发·毕业设计·毕设
ooo-p1 天前
FPGA学习篇——Verilog学习之寄存器的实现
学习·fpga开发
北京青翼科技1 天前
【PCIE711-214】基于PCIe总线架构的4路HD-SDI/3G-SDI视频图像模拟源
图像处理·人工智能·fpga开发·信号处理
G皮T1 天前
【弹性计算】异构计算云服务和 AI 加速器(四):FPGA 虚拟化技术
阿里云·fpga开发·云计算·虚拟化·fpga·异构计算·弹性计算
落笔太慌张~2 天前
[FPGA基础学习]实现流水灯与按键暂停
fpga开发
坚持每天写程序2 天前
Processor System Reset IP 核 v5.0(vivado)
fpga开发
相醉为友2 天前
001 使用单片机实现的逻辑分析仪——吸收篇
笔记·单片机·嵌入式硬件·fpga开发·嵌入式