Embedded Files
VHDL Design Units
VHDL Design Units
Entity
- construct that in simple terms, lists the various inputs and outputs of the underlying circuitry
- port name x is an identifier used to differentiate the various signals.
- Each port name is unique and has an associated mode and data type. This is a requirement
- in, out, or inout specifies the direction of the signal relative to the entity where signals can either enter, exit or do both
- std_logic refers to the type of data that the port will handle
- bundles(bus signals) use std_logic_vector data type to indicate that each signal name contains more than one signal.
VHDL Standard Libraries
Architecture
- data-flow model
- behavioral model
- structural model
- hybrid model (combination of the three)
Signal and Variable Assignments
- Object Types:
- signal - software representation of a wire
- " <=" to assign new value
- variable - like in C or Java, is used to store local information
- “:=”t o assign new value
- constant - like a variable type, but its value cannot be changed
- signal - software representation of a wire
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