Register Transfer Language -2
The symbolic notation used to describe the microoperation transfers among registers is called a register transfer language. The term "register transfer" implies the availability of hardware logic circuits that can perform a stated microoperation and transfer the result of the operation to the same or another register.The word "language" is borrowed from programmers, who apply this term to programming languages. A programming language is a procedure for writing symbols to specify a given computational process. Similarly, a natural language such as English is a system for writing symbols and combining them into words and sentences for the purpose of communication between people. A register transfer language is a system for expressing in symbolic form the microoperation sequences among the registers of a digital module. It is a convenient tool for describing the internal organization of digital computers in concise and precise manner. It can also be used to facilitate the design process of digital systems.
The register transfer language adopted here is believed to be as simple as possible, so it should not take very long to memorize. We will proceed to define symbols for various types of microoperations, and at the same time, describe associated hardware that can implement the stated microoperations. The symbolic designation introduced in this chapter will be utilized in subsequent chapters to specify the register transfers, the microoperations, and the control functions that describe the internal hardware organization of digital computers. Other symbology in use can easily be learned once this language has become familiar, for most of the differences between register transfer languages consist of variations in detail rather than in overall purpose.