![]() ![]() We only need to use these keywords if we wish to modify this default behaviour. This means that we can assign negative numbers to these signals.īy default, the integer type is signed whilst both the reg and wire types are unsigned. When we declare a type as signed in verilog, it is interpreted as a 2's complement number. This allows us to change the way our variable interprets data. However, the signed and unsigned keywords were introduced as a part of the verilog 2001 standard. Similarly, the integer type was always interpreted as a signed value. Prior to the release of the verilog 2001 standard all variable and net types could only be used to store unsigned data types. The code snippet below shows how we declare and assign an integer type in verilog. For example, if we declare an integer constant with a value of 255 then our synthesis tool will trim this down to 8 bits. ![]() Our synthesis tools will automatically trim any unused bits in our integer type. When we use an integer type, we assign numerical rather than binary values to the variable.Īs we can also assign numeric values to the reg type, we typically use integers for constants or loop variables in verilog. However, we normally use this for internal signals in a module rather than for ports.īy default, the integer is a 32 bit 2s complement number which we can use to represent any whole number in our verilog design. The most commonly used type for numerical data in verilog is the integer type. Let's take a closer a look at both of these types. In verilog, there are two commonly used numeric types - the integer type and the real type. However, we can also represent data numerically in our verilog designs. The types which we have looked at so far are all used with single bits of data. The code snippet below shows this general syntax. We use the same syntax to declare a variable in verilog, regardless of the exact type. These four different values are shown in the table below. Regardless of the exact type we are using, there are four valid values we can assign to individual bits in our data. These types can store data, meaning that their behaviour is similar to variables in other programming languages such as C. We primarily use the variable types to model registers or flip flops in our design. ![]() They are unable to store values on their own and must be driven with data. We use the net types to model connections in our digital circuits. We use these two different groups to model different elements of our digital circuits. The code snippet below shows the general syntax for representing digital data in verilog.īroadly speaking, the basic data types in verilog can be split into two main groups - net types and variable types. Therefore, we can create data busses which contain as many bits as we choose. This is because we are fundamentally describing hardware circuits when we use verilog. Unlike in other programming languages, we also need to define the number of bits we have in our data representation. ![]() We can express this data as either a binary, hexadecimal or octal value. When we write verilog, we often need to represent digital data values in our code. As a result, there is often no need necessary to explicitly perform type conversions in verilog. When we assign data to a signal in verilog, the data is implicitly converted to the correct type in most cases. We can also use types which interpret our data as if it were a numeric value. We can use types which interpret data purely as logical values, for example. The type which we specify is used to define the characteristics of our data. This includes a discussion of data respresentation, net types, variables types, vectors types and arrays.Īlthough verilog is considered to be a loosely typed language, we must still declare a data type for every port or signal in our verilog design. In this post, we talk about the most commonly used data types in Verilog. ![]()
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