Contents
Why we use std logic in VHDL?
The most common type used in VHDL is the std_logic . Think of this type as a single bit, the digital information carried by a single physical wire. The std_logic gives us a more fine-grained control over the resources in our design than the integer type, which we have been using in the previous tutorials.
What is downto in VHDL?
Most VHDL designers write ‘something downto something’ in their code all the time. The keywords downto and to specify the direction of ranges in VHDL. downto is descending (going down); to is ascending (going up).
What is the difference between std_logic_vector and std_logic?
Std_logic signals represent one data bit and std_logic_vector represents several data bits. The signal assignments for standard logic and standard logic vector data types are shown in Example 1-15. The number of data bits for a std_logic_vector is defined in the signal assignment statement.
What is meant by std_logic_vector?
The VHDL keyword “std_logic_vector” defines a vector of elements of type std_logic. For example, std_logic_vector(0 to 2) represents a three-element vector of std_logic data type, with the index range extending from 0 to 2.
What does 0 mean in VHDL?
The statement “Others => ‘0’” is a feature of the VHDL when the coder want to defined several items in an array with the same value. In your example, all item std_logic in the array are set to ‘0’.
What is Std_ulogic?
The std_ulogic is simply an enumerated type which lists the possible values as enumeration literals. When a signal or variable is declared with std_ulogic as the type, it can represent any one of these values, and none other. The ‘U’ value is the first of the listed values.
What’s the difference between std logic and std _ logic _ vector?
To generate this code they have some template and to make their template configurable they create ability to change some static variables. For example, they write it as std_logic_vector (m-1 downto 0) and user can change m in GUI, so if user puts m=1, the auto generated code will has std_logic_vector (0 downto 0).
Is the write enable of the Ram std _ logic?
The problem is that the write enable of the RAM is defined as an std_logic_vector (0 down to 0) instead as a std_logic and I do not know how to connect them. In the test bench I wrote for testing the connection I defined a signal for establishing the communication between the two of them:
How to cast CIN to std _ logic in VHDL?
It should just have been a simple std_logic. You need to cast cin to an unsigned, then add it in. Note that resize returns an unsigned here. The following is a simplification of your design that meets all the requirements and compiles in VHDL-93 onwards.
How to test the connection between STD and STD?
In the test bench I wrote for testing the connection I defined a signal for establishing the communication between the two of them: So far things are great, the problem comes when I try to map the write_en_b34 signal to the wea port.