Transaction Level Modeling: An Overview Lukai Cai and Daniel Gajski Center for Embedded Computer Systems University of California, Irvine Irvine, CA 92697, USA {lcai,gajski}@cecs.uci.edu ABSTRACT Recently, the transaction-level modeling has been widely re- ferred to in system-level design community. However, the transaction-level models(TLMs) are not well defined and the usage of TLMs in the existing design domains, namely mod- eling, validation, refinement, exploration, and synthesis, is not well coordinated. This paper introduces a TLM taxon- omy and compares the benefits of TLMs’ use. Categories and Subject Descriptors C.0 [Computer Systems Organization]: General General Terms Design Keywords Transaction level model, modeling, validation, refinement, exploration, synthesis 1. INTRODUCTION In order to handle the ever increasing complexity of system- on-chips (SoCs) and time-to-market pressures, the design abstraction has been raised to the system level in order to increase design productivity. This higher level of abstrac- tion generated large interest in transaction-level modeling, synthesis, and verification [10][12]. In a transaction-level model (TLM), the details of com- munication among computation components are separated from the details of computation components. Communica- tion is modeled by channels, while transaction requests take place by calling interface functions of these channel models. Unnecessary details of communication and computation are hidden in a TLM and may be added later. TLMs speed up simulation and allow exploring and validating design alter- natives at the higher level of abstraction. However, the definition of TLMs is not well understood. Without clear definition of TLMs, not only the predefined Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. CODES+ISSS’03, October 1–3, 2003, Newport Beach, California, USA. Copyright 2003 ACM 1-58113-742-7/03/0010 ...$5.00. Computation Communication A B C D F Un- timed Approximate- timed Cycle- timed Un- timed Approximate- timed Cycle- timed A. Specification model B. Component-assembly model C. Bus-arbitration model D. Bus-functional model E. Cycle-accurate computation model F. Implementation model E Figure 1: System modeling graph TLMs cannot be easily reused, but also the usage of TLMs in the existing design domains, namely modeling, validation, refinement, exploration, and synthesis, cannot be systemat- ically developed. Consequently, the inherent advantages of TLMs don’t effectively benefit designers. In order to elim- inate some ambiguity of TLMs, this paper attempts to ex- plicitly define several transaction-level models, each of which is adopted for different design purpose. It also explores the usage of defined TLMs under a general design flow and an- alyzes how the TLMs are used in the design domains. This paper is organized as follows: Section 2 reviews the related work; Section 3 defines four TLMs; Section 4 in- troduces the usage of TLMs in different design domains; Finally, the conclusion is given in section 5. 2. RELATED WORK The concept of TLM first appears in system level lan- guage and modeling domain. [10] defines the concept of a channel, which enables separating communication from computation. It proposes four well-defined models at differ- ent abstraction levels in a top-down design flow. Some of these models can be classified as TLMs. However, the capa- bilities of TLMs are not explicitly emphasized. [12] broadly describes the TLM features based on the channel concept and presents some design examples. However, the TLMs are not well defined and the usage of TLMs in the existing design domains is not addressed. [10] [12] also demonstrate that both SpecC [3] and SystemC [2] support transaction level modeling using the channel concept. The TLMs can be used in top-down approaches such as 19