cpe229_lec10

Cpe229_lec10 - CPE 229 Course Notes Lecture 10 Copyright 2005 Bryan Mealy More on Microoperations One of the main features of the previous set of

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CPE 229 Course Notes: Lecture 10 Copyright: 2005 Bryan Mealy More on Microoperations One of the main features of the previous set of notes was the introduction of the microoperation. In this context, a microoperation was defined as an elementary operation that is performed on data stored in registers. The thing to keep in mind here is that registers have the ability to perform elementary operations. When a register performs one of these elementary operations, it is considered to be performing a microoperation. Although we mentioned several types of microoperations in the previous set of notes in order to get your feet wet, we’ll introduce more micro operations in this set of notes but we’ll divide them into specific types. The reality is that the types listed are somewhat arbitrary. Not only do they not include every possible microoperation ever possible on any piece of hardware, some of the microoperations listed can fall into more than one of the listed types. Some of the instructions that can logically fit into more than one category will be duly noted. The following classification then is mostly for instructional purposes so don’t try to read too much into it. The four major types of microoperations can be classified as follows: Transfers – data is not changed as data passes from one register to another Arithmetic – some arithmetic function is performed on data in registers Logic – some logical-type bitwise manipulation is performed on data in the registers Shift – the change in register data can be characterized by a shift in the data Transfer Microoperations: This type of microoperation was discussed in the last set of notes. While this could be considered the most straight-forward form of microoperation, it is rarely the most useful. A typical transfer microoperation is represented by the RTL statement shown in Equation 1. In this equation, the contents of register R2 are transferred to register R1 under the condition that X is asserted. This transition, as are most all microoperation represented by RTL, is synchronized to some clock edge. By convention, the clock is rarely listed in the RTL equation. X : R1 R2 Equation 1: A typical transfer microoperation. Arithmetic Microoperations: There are a few standard arithmetic microoperations that everyone knows and loves. You’ve grown used to using these in many aspects of everyday computer life but you probably did not realize these functions had their roots in RTL-space. Some of the more popular arithmetic microoperations are shown in Table 1. The most important thing to remember about the microoperations listed in this table is that writing the equation means that you can either currently perform the operation (the hardware, in this case some arithmetic circuit, exists) or you’ll soon be able to perform the operation (you’re designing the hardware capable of performing the given function). It’s sort of a wicked relationship but it is quite useful and you’ll see it over an over again this quarter. I tried to describe some example
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This note was uploaded on 03/27/2009 for the course CPE 229 taught by Professor Smith during the Spring '09 term at Cal Poly.

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Cpe229_lec10 - CPE 229 Course Notes Lecture 10 Copyright 2005 Bryan Mealy More on Microoperations One of the main features of the previous set of

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