1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities@ IEC publishes International Standards@ Technical Specifications@ Technical Reports@ Publicly Available Specifications (PAS) and Guides (hereafter referred to as ??IEC Publication(s)??). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International@ governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.2) The formal decisions or agreements of IEC on technical matters express@ as nearly as possible@ an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees. 3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate@ IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user.4) In order to promote international uniformity@ IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with an IEC Publication.6) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.International Standard IEC/IEEE 62050 has been processed through IEC technical committee 93: Design automation.This standard defines a subset of very high-speed integrated circuit hardware description language (VHDL) that ensures portability of VHDL descriptions between register transfer level synthesis tools. Synthesis tools may be compliant and yet have features beyond those required by this standard. This standard defines how the semantics of VHDL shall be used@ for example@ to model level-sensitive and edge-sensitive logic. It also describes the syntax of the language with reference to what shall be supported and what shall not be supported for interoperability.Use of this standard should minimize the potential for functional simulation mismatches between models before they are synthesized and after they are synthesized.