[吾题有解] HDLBits : Lemmings3

只要完成了旅鼠2旅鼠3的逻辑会更加清晰。其实原文中的一句话已经把整个状态机的组合逻辑判断部分写的很清楚了。In other words, a walking Lemming can fall, dig, or switch directions. If more than one of these conditions are satisfied, fall has higher precedence than dig, which has higher precedence than switching directions.也就是在组合逻辑判断部分我们只需要按照这句话的描述使用三目运算符将优先级高的输入信号放在判断部分满足则进入高优先级行为不满足则进入低优先级行为低优先级行为可以嵌套判断更低优先级的行为。唯一需要说明的是为什么Dig状态需要两个旅鼠在挖通地面后ground 0会进入到下落状态而下落状态是区分方向的这个方向取决于旅鼠在开挖之前是向左走状态还是向右走状态故而虽然挖掘本身不带方向却隐含着“由哪个方向转化而来”的属性这与之前的一道蓄水池有限状态机中的思想类似大家可以参考我的这篇博客HDLBits : Exams/ece241 2013 q4里边有详细解释。最后贴出Verilog HDL代码供大家参考moduletop_module(input clk,input areset,// Freshly brainwashed Lemmings walk left.input bump_left,input bump_right,input ground,input dig,output walk_left,output walk_right,output aaah,output digging);localparam LEFT0,RIGHT1,FALL_L2,FALL_R3,DIG_L4,DIG_R5;reg[2:0]state;reg[2:0]next_state;always (posedge clk or posedge areset)if(areset)stateLEFT;elsestatenext_state;always (*)begincase(state)LEFT:next_state~ground?FALL_L:(dig?DIG_L:(bump_left?RIGHT:LEFT));RIGHT:next_state~ground?FALL_R:(dig?DIG_R:(bump_right?LEFT:RIGHT));FALL_L:next_stateground?LEFT:FALL_L;FALL_R:next_stateground?RIGHT:FALL_R;DIG_L:next_state~ground?FALL_L:DIG_L;DIG_R:next_state~ground?FALL_R:DIG_R;endcase end assign walk_left(stateLEFT);assign walk_right(stateRIGHT);assign aaah(stateFALL_L)||(stateFALL_R);assign digging(stateDIG_L)||(stateDIG_R);endmodule