vhdl, Synthesis question: Records and InOut ports

In this package the enumerated type SimConditionType, to be used to select Worst, Typical or Best Case values for timing parameters in VHDL models for board-level simulation. (vhd file available)

If VIOLATED, we should go back tothe VHDL code and re-write it to improve timing.

This document provides recommendations for development and usage of VHDL models intended for Board-level simulation. The purpose of these recommendations is to define modelling criteria that will produce models that are highly accurate in both functionality and timing, and that will provide sufficient simulation performance to facilitate long simulation runs.

VHDL Physical Type is not Synthesizable, or is it

It is importantthat a designer knows both of them although we are using only VHDL in class.

A digital system in VHDL consists of a design entitythat can contain other entities that are then considered components of thetop-level entity. Each entity is modeled by an and an. One can consider the entity declaration as theinterface to the outside world that defines the input and output signals, whilethe architecture body contains the description of the entity and is composed ofinterconnected entities, processes and components, all operating concurrently,as schematically shown in Figure 3 below. In a typical design there will bemany such entities connected together to perform the desired function.

Resources for Electrical Engineers

In order to overcome the limitations of the classical 'dataflow' design style (large number of concurrent VHDL statements and processes, leading to bad readability and increased simulation time), a 'two-process' coding method is proposed: one process contains all combinational logic, whereas the other process infers all (and only) the registers. The paper further introduces the use of record types to increase readability and the safe use of variables to reduce simulation time. The method has been applied on several designs made by or for ESA. A presentation/lecture is also available.


The VHSIC Hardware Description Language (VHDL) is a formal notation intended for use in all phases of the creation of electronic systems. Because it is both machine readable and human readable, it supports the development, verification, synthesis, and testing of hardware designs, the communication of hardware design data, and the maintenance, modification, and procurement of hardware.

VHDL records as ports - Community Forums

VHDL stands for VHSIC (Very High SpeedIntegrated Circuits) Hardware Description Language. In themid-1980’s the U.S. Department of Defense and the IEEE sponsored thedevelopment of this hardware description language with the goal to develop veryhigh-speed integrated circuit. It has become now one of industry’s standardlanguages used to describe digital systems. The other widely used hardwaredescription language is Verilog. Both are powerful languages that allow you todescribe and simulate complex digital systems.A third HDL language is ABEL (Advanced Boolean Equation Language) whichwas specifically designed for Programmable Logic Devices (PLD). ABEL is lesspowerful than the other two languages and is less popular in industry. Thistutorial deals with VHDL, as described by the IEEE standard 1076-1993.

To Design a Half adder and Full adder using VHDL programming ..

Aside from user defined types for state machine
description, I don't see any encouragement from the press or tool vendors to
use any VHDL type other than std_logic.