cpe229_lec23 - CPE 229 Course Notes: Lecture 23 Copyright:...

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CPE 229 Course Notes: Lecture 23 Copyright: 2005 Bryan Mealy And Yet, Even More I/O Stuff The ability for a computer to input and output information is what makes computers useful. The added benefit is that they do it relatively fast. And the really cool thing is that the concepts involved in doing such interfacing are straightforward enough so any engineering or computer science student can design and implement microcontroller-based systems with relative ease. Scientific studies have proven this fact to be true in all technical settings. The tendency in some computer science students is to consider digital design a pure hardware pursuit. A similar tendency in some engineering majors (probably not computer engineering majors) is to consider digital design a pursuit that requires a bunch of programming in order to accomplish anything useful. The thought of programming something most likely elicits bad memories from classes taken using a higher level language (such as Java) and developing a slew of time consuming and pointless programs. Neither of these views is completely accurate. The reality is that digital system design at the microcontroller level is straightforward for just about anyone who has the courage not to be intimidated by the concepts, the instruction sets, the programmers models, and most of all, the associated datasheets. This set of notes represents another example of the steps that would be required in order to interface the PicoBlaze microcontroller with a peripheral device. In this context, a peripheral device is some device external to PicoBlaze that provides some sore of information regarding the outside world (generally a sensor of some sort). As you probably remember from the previous set of notes, PicoBlaze has been designed in a generic manner so as to be able to interface to just about any digital device out there. This generic approach to microcontrollers is essential due to the fact that there are so many digital devices out there and most all of them are easily controlled with a microcontroller. This set of notes describes the interfacing requirements for a relatively generic analog-to-digital converter (ADC). Despite the fact that these notes are somewhat specific to an ADC, try to keep in touch with the fact that steps involved are somewhat generic and can be used as a road map to interfacing any device. Keep in mind that there are only three basic steps in this process once you’ve identified the device you intend to interface with. These steps are listed below. 1. Define device interface requirements: Once you’ve decided upon the device you’ll be working with, you need to read through the datasheet in order to define which signal on the device will be used to communicate with the microcontroller. These signals are essentially control and status signal: the control signals are used to control the peripheral device and the status signals are used to communicate status information to the microcontroller. The control and status signals are
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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_lec23 - CPE 229 Course Notes: Lecture 23 Copyright:...

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