SpinalEnum

一、描述(Description)

Enumeration类型代表一组值组成的列表

二、声明(Declaration)

枚举数据类型的声明方式如下：

object Enumeration extends SpinalEnum {
    val element0, element1, ..., elementN = newElement()
}

对于上述例子, 使用默认的编码方式。原生的枚举类型用于VHDL, 二进制编码用于Verilog。

能够通过下述方式强制使用枚举编码：

object Enumeration extends SpinalEnum(defaultEncoding=encodingOfYourChoice) {
    val element0, element1, ..., elementN = newElement()
}

备注：如果想为给定的模块定义枚举类型的输入/输出, 应该用如下方式定义：in(MyEnum())或者out(MyEnum)

1. 编码(Encoding)

   SpinalHDL支持下述的枚举编码方式：

编码方式	Bit位宽	描述
native		这是默认编码方式, 使用VHDL枚举系统
binarySequential	log2Up(stateCount)	以声明的顺序使用Bits存储状态(值从0到n-1)
binaryOneHot	stateCount	使用Bits来存储状态, 每个bit对应一个状态

定制化的编码方式能用静态和动态的方式实现：

/*
 *静态编码方式
 */
object MyEnumStatic extends SpinalEnum {
    val e0, e1, e2, e3 = newElement()
    defaultEncoding = SpinalEnumEncoding("staticEncoding")(
        e0 -> 0,
        e1 -> 2,
        e2 -> 3,
        e3 -> 7
    )

/*
 *用函数动态编码： _ * 2 + 1
 *e.g. :  e0 => 0 * 2 + 1 = 1
 *        e1 => 1 * 2 + 1 = 3
 *        e2 => 2 * 2 + 1 = 5
 *        e3 => 3 * 2 + 1 = 7
 */
    val encoding = SpinalEnumEncoding("dynamicEncoding", _ * 2 + 1)

    object MyEnumDynamic extends SpinalEnum(encoding) {
        val e0, e1, e2, e3 = newElement()
    }
}

1. 举例(Example)

   初始化枚举信号并给它赋值：

   object UartCtrlTxState extends SpinalEnum {
       val sIdle, sStart, sData, sParity, sStop = newElement()
   }
   
   val stateNext = UartCtrlTxState()
   stateNext := UartCtrlTxState.sIdle
   
   //你也可以import枚举类型使其元素可视化, 需要放在package里
   import UartCtrlTxState._
   stateNext := sIdle
   

   Verilog:

   localparam UartCtrlTxState_sIdle = 3'd0;
   localparam UartCtrlTxState_sStart = 3'd1;
   localparam UartCtrlTxState_sData = 3'd2;
   localparam UartCtrlTxState_sParity = 3'd3;
   localparam UartCtrlTxState_sStop = 3'd4;
   
   wire       [2:0]    stateNext;
   
   `ifndef SYNTHESIS
       reg [55:0] stateNext_string;
   `endif
   
   
   `ifndef SYNTHESIS
       always @(*) begin
           case(stateNext)
           UartCtrlTxState_sIdle : stateNext_string = "sIdle  ";
           UartCtrlTxState_sStart : stateNext_string = "sStart ";
           UartCtrlTxState_sData : stateNext_string = "sData  ";
           UartCtrlTxState_sParity : stateNext_string = "sParity";
           UartCtrlTxState_sStop : stateNext_string = "sStop  ";
           default : stateNext_string = "???????";
           endcase
       end
   `endif
   
   assign stateNext = UartCtrlTxState_sIdle;
   

三、操作符(Operators)

以下是可供Enumeration类型使用的操作符：

1. 比较运算(Comparison)

   |操作符|描述|返回类型| |x===y|相等|Bool| |x=/=y|不相等|Bool|

   import UartCtrlTxState._
   
   val stateNext = UartCtrlTxState()
   stateNext := sIdle
   
   when(stateNext === sStart) {
       ...
   }
   
   switch(stateNext) {
       is(sIdle) {
           ...
       }
       is(sStart) {
           ...
       }
       ...
   }
   

2. 类型(Types)

   为了使用你的enum, 例如在函数里, 你需要它的类型。

   enum中值的类型(例如sIdle的类型)：

   spinal.core.SpinalEnumElement[UartCtrlTxState.type]
   

   或者等价地, 也可以如下方式

   UartCtrlTxState.E
   

   bundle的类型(例如stateNext的类型)：

   spinal.core.SpinalEnumCraft[UartCtrlTxState.type]
   

   或者等价地, 也可以用如下方式

   UartCtrlTxState.C
   

3. 类型转换(Type cast)

操作符	描述	返回类型
x.asBits	二进制转换为Bits	Bits(w(x) bits)
x.asUInt	二进制转换为UInt	UInt(w(x) bits)
x.asSInt	二进制转换为SInt	SInt(w(x) bits)
e.assignFromBits(bits)	Bits转换为enum	MyEnum()

import UartCtrlTxState._

val stateNext = UartCtrlTxState()
myBits := sIdle.asBits

stateNext.assignFromBits(myBits)

Verilog:

localparam UartCtrlTxState_sIdle = 3'd0;
localparam UartCtrlTxState_sStart = 3'd1;
localparam UartCtrlTxState_sData = 3'd2;
localparam UartCtrlTxState_sParity = 3'd3;
localparam UartCtrlTxState_sStop = 3'd4;

wire       [2:0]    myBits;
wire       [2:0]    stateNext;
wire       [2:0]    _zz_stateNext;
reg        [7:0]    counter;
`ifndef SYNTHESIS
    reg [55:0] stateNext_string;
    reg [55:0] _zz_stateNext_string;
`endif


`ifndef SYNTHESIS
    always @(*) begin
        case(stateNext)
            UartCtrlTxState_sIdle : stateNext_string = "sIdle  ";
            UartCtrlTxState_sStart : stateNext_string = "sStart ";
            UartCtrlTxState_sData : stateNext_string = "sData  ";
            UartCtrlTxState_sParity : stateNext_string = "sParity";
            UartCtrlTxState_sStop : stateNext_string = "sStop  ";
            default : stateNext_string = "???????";
        endcase
    end
    always @(*) begin
        case(_zz_stateNext)
            UartCtrlTxState_sIdle : _zz_stateNext_string = "sIdle  ";
            UartCtrlTxState_sStart : _zz_stateNext_string = "sStart ";
            UartCtrlTxState_sData : _zz_stateNext_string = "sData  ";
            UartCtrlTxState_sParity : _zz_stateNext_string = "sParity";
            UartCtrlTxState_sStop : _zz_stateNext_string = "sStop  ";
            default : _zz_stateNext_string = "???????";
        endcase
    end
`endif

assign myBits = UartCtrlTxState_sIdle;
assign _zz_stateNext = myBits;
assign stateNext = _zz_stateNext;