OverviewAn enum defines a new type with a set of scalar values with symbolic names.
Syntax typedef enum {Identifier1, Identifier2, ... IdentifierN} EnumName
deriving (Eq, Bits);
- Enum label identifiers must begin with Uppercase letters
- Enum labels can be repeated in different enum definitions
- The default decoding of labels is 0,1,2..., using just enough bits to encode the entire set
- deriving Bits allows this structure to be used and converted to type Bits. This means it can be used by Reg#() and all data functions and types that use Bit as an input.
- deriving Eq allows this type to be compared with ==. Just do a straight compare of all the bits in each data bus.
Examples typedef enum{Green, Yellow, Red} TrafficLight deriving (Eq, Bits);
typedef enum{Reset, Count, Decision} States deriving (Eq, Bits);
Using Enums- A defined enum type is used like any other type: to declare variables, function/module parameters, etc.
- The enum labels are used as constant values of that type
Example: Comparing Enum values
TrafficLight t1 = Red;
TrafficLight t2 = Yellow;
if (c1 == Red)
...
if (c1 == c2)
...
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