Naturalized Communication and Testing

Abstract

We "naturalize" the handshake communication links of a self-timed system by assigning the capabilities of filling and draining a link and of storing its full or empty status to the link itself. This contrasts with assigning these capabilities to the joints, the modules connected by the links, as was previously done. Under naturalized communication, the differences between Micropipeline, GasP, Mousetrap, and Click circuits are seen only in the links -the joints become identical; past, present, and future link and joint designs become interchangeable.We also "naturalize" the actions of a self-timed system, giving actions status equal to states -for the purpose of silicon test and debug. We partner traditional scan test techniques dedicated to state with new test capabilities dedicated to action. To each and every joint, we add a novel proper-start-stop circuit, called MrGO, that permits or forbids the action of that joint. MrGO, pronounced "Mister GO," makes it possible to (1) exit an initial state cleanly to start circuit operation in a delay-insensitive manner, (2) stop a running circuit in a clean and delay-insensitive manner, (3) single-or multi-step circuit operations for test and debug, and (4) test sub-systems at speed.

Drafting in Self-Timed Circuits

“…In Click [20], as realized in [21], the key decision gate is the NAND (Figure 47 Mousetrap [22], as realized in [3] is shown in Figure 48. A general principle can be derived from the decision gates examined here.…”

“…presence of a token, and its output or "successor" state-wire is low, indicating a space or "vacancy". This condition produces a pulse on the fire signal that advances the token [3,4]. Tokens can change their spacing on the FIFO but not their sequence.…”

Formal Verification of Mixed Synchronous Asynchronous Systems Using Industrial Tools

“…• Roncken et al [13] use go signals to control progress in asynchonrous circuits in a fine-grained manner for the purpose of silicon test and debug. The idea is further developed in [14], where go signals are used to model non-determinism in asynchonrous circuits in the context of formal verification of link-joint models using the theorem proving system ACL2.…”

Modular Timing Constraints for Delay-Insensitive Systems

“…Avoiding over-specification is important and harder than one might think. We inadvertently and repeatedly over-specified the handshake behavior of a component using the approach in [45], [52], which requires complete specifications in CCS Figure 4 Organization of the model checking task to verify, for a given handshake component, that the component's circuit in its environment and under its timing constraints satisfies both the gate-level "digital health" properties and the properties defined by the component's protocol. Examples of "digital health" are semimodularity, used later in this paper, and absence of set-reset drive fights, which plays no role in this paper.…”

“…We chose and2.val+ as p's myPOD rather than FF.q±, because as the AND function of the Click Storage component, and2.val+ makes the component "act" more so than FF.q±. Moreover, alternative circuit implementations that split FF into separate flipflops for each channel[52] require p to use and2.val+ as myPOD. Having said that, the Click Storage circuit inFigure 1(right-column-top) can use FF.q± as myPOD and thus, without inserting an additional checkpoint, avoid the need to differentiate rising from falling transitions in myEARLY.…”