CASL - A language for automating the implementation of computer architectures

The computer Architecture Specification Language (CASL), described in this paper, is intended for use by computer architects CASL is a state machine description language especially useful for describing digital systems at the "register transfer" level and designed to meet the needs of the computer architect as a design and documentation medium. A machine described in CASL may be decomposed into cooperating Modules, each representing an asynchronous finite state machine. Each Module consiste of an Abstractions, Structure, and Procedure section. An architect may use the Abstractions section to define his own data representations and primitive operations. The Structure section describes structural elements section describes structural elements (combinatorial and sequential hardware "building blocks") and connections (explicit specifications of each data path). The Procedure section is a textual (nearly ALGOL-like) representation of the state transition graph and the sets of control signals issued concurrently in each state to drive the structure. Statements in each state are collateral, rather than sequential, and CASE structures are used for conditional selection of control signals to be issued by a state. A macro facility is provided to encode groups of control signals.