Lec17 - Such behaviors may be either sequential or...

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System Specifications and Modeling Lecture 17
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Last Lecture Timing Embedded system specifications Overview of design languages
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Today's Lecture HDL Limitations SpecCharts Language
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We determined five characteristics common to embedded systems: sequential and concurrent behavior decomposition, state transitions, Exceptions, sequential algorithms, behavior completion.
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Unfortunately, no existing language supports all five characteristics. We say a language “‘supports” a characteristic if there is a simple, direct mapping of the characteristic to a language construct. A lack of support does not mean that the characteristic cannot be described, but instead means that the characteristic cannot be described easily.
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HDL Limitations Sequential and Concurrent Behavior Decomposition To cope with the complexity of system functionality, we usually need to hierarchically decompose functionality into simpler pieces, or behaviors.
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Unformatted text preview: Such behaviors may be either sequential or concurrent to one another, and may themselves be further decomposed. VHDL supports sequential decomposition using procedures, but it only partially supports concurrent decomposition. In particular, VHDL supports concurrent decomposition of a systems top-level functionality using processes, but does not support concurrent decomposition of a process or procedure, i.e., forking is not directly supported. Forking in VHDL It should be noted that a person reading the VHDL description will initially be misled into believing that the system is composed of three concurrent behaviors, Main, Q. and R. State Transitions Coerce description of state transition in VHDL Exceptions Coerce description of exceptions in VHDL Using Spec charts...
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Lec17 - Such behaviors may be either sequential or...

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