SpinalHDL语法之Bool类型

作为SpinalHDL语法篇的第一节，我们也从最简单的开始。

Bool类型定义

Bool类型就是Verilog中的单bit类型，定义方式如下：

Syntax	Description	Return
Bool()	创建Bool类型变量	Bool
True	创建Bool类型变量，并赋值true	Bool
False	创建Bool类型变量，并赋值false	Bool
Bool(value: Boolean)	创建Bool类型变量，并使用Scala表达式赋值	Bool

Example：

val a = Bool()
val b = True
val c = False
val d = Bool( 1 > 2)

生成的Verilog代码如下：

wire                a;
wire                b;
wire                c;
wire                d;

assign b = 1'b1;
assign c = 1'b0;
assign d = 1'b0;

逻辑运算

下图为官方的逻辑运算解释，也不翻译了，很容易理解。

Operator	Description	Return type
!x	Logical NOT	Bool
x && y	Logical And	Bool
x & y	Logical And	Bool
x		y
x	y	Logical OR
x ^ y	Logical XOR	Bool
x.set[()]	Set x to True	Bool
x.clear[()]	Set x to False	Bool
x.setWhen(cond)	Set x when cond is True	Bool
x.clearWhen(cond)	Clear x when cond is True	Bool
x.riseWhen(cond)	Set x when x is False and cond is True	Bool
x.fallWhen(cond)	Clear x when x is True and cond is True	Bool

val e = a & b
  val f = a | b
  val g = a ^ b
  val h = !a

  val i = Bool()
  i.set()
  val j = Bool()
  j.clear()

  val k = True #这里必须有初值，否则下一句会报错
  k.clearWhen(b)

  val l = True
  when(b){
    l := False
  }

  val m = RegInit(False) #关于寄存器类型，这里先熟悉一下，后面章节会讲到
  m.riseWhen(b)

边缘检测

Operator	Description	Return type
x.edge[()]	Return True when x changes state	Bool
x.edge(initAt: bool)	Same as x.edge but with a reset value	Bool
x.rise[()]	Return True when x was low at the last cycle and is now high	Bool
x.rise(initAt: Bool)	Same as x.rise but with a reset value	Bool
x.fall[()]	Return True when x was high at the last cycle and is now low	Bool
x.fall(initAt: Bool)	Same as x.fall but with a reset value	Bool
x.edges[()]	Return a bundle (rise, fall, toggle)	BoolEdges
x.edges(initAt: Bool)	Same as x.edges but with a reset value	BoolEdges

val a = Bool()
val b = False
when(a.edge()){
b := True
}
val c = a.edge(False)

转换后的代码为：

module DemoBool (
  input               clk,
  input               reset
);

  wire                a;
  reg                 b;
  reg                 a_regNext;
  wire                when_DemoBool_l35;
  reg                 a_regNext_1;
  wire                c;

  always @(*) begin
    b = 1'b0;
    if(when_DemoBool_l35) begin
      b = 1'b1;
    end
  end

  assign when_DemoBool_l35 = (a ^ a_regNext);
  assign c = (a ^ a_regNext_1);
  always @(posedge clk) begin
    a_regNext <= a;
  end

  always @(posedge clk or posedge reset) begin
    if(reset) begin
      a_regNext_1 <= 1'b0;
    end else begin
      a_regNext_1 <= a;
    end
  end

endmodule

val edgeBundle = myBool_2.edges(False)
when(edgeBundle.rise) {
    // do something when a rising edge is detected
}
when(edgeBundle.fall) {
    // do something when a falling edge is detected
}
when(edgeBundle.toggle) {
    // do something at each edge
}

数值比对

Operator	Description	Return type
x === y	Equality	Bool
x =/= y	Inequality	Bool