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Using An Educational Microprocessor Architecture And Fpga Implementation To Introduce Interrupts

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Conference

2008 Annual Conference & Exposition

Location

Pittsburgh, Pennsylvania

Publication Date

June 22, 2008

Start Date

June 22, 2008

End Date

June 25, 2008

ISSN

2153-5965

Conference Session

Hardware Descriptive Language Education

Tagged Division

Computers in Education

Page Count

12

Page Numbers

13.1328.1 - 13.1328.12

Permanent URL

https://peer.asee.org/4173

Download Count

23

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Paper Authors

biography

Jonathan Hill University of Hartford

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Dr. Jonathan Hill is an assistant professor on Electrical and Computer Engineering in the College of Engineering, Technology, and Architecture (CETA) at the University of Hartford, located in Connecticut. Ph.D. and M.S. from Worcester Polytechnic Institute (WPI) and Bachelor's degree from Northeastern University. Previously an applications engineer with the Networks and Communications division of Digital Corporation. His interests involve embedded microprocessor based systems.

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Abstract
NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Using an Educational Microprocessor Architecture and FPGA Implementation to Introduce Interrupts Abstract

The use of interrupts is an important topic in the use of computers. Interrupts provide the means for a computer to quickly respond to significant real-world events. Unlike polling, which is suitable for interfacing slow peripherals, interrupts provide a more efficient means to interface with devices. Interrupts are generally considered to be advanced and unfortunately, the topic can be a challenge to present to students. In computer architecture in particular, the topic of interrupts is often overly abstracted, which can make learning about interrupts difficult for students.

Following a trigger event, an interrupt service routine (ISR) is invoked to provide service. Such an event could be the arrival of data on a serial communications port, or a signal that the brakes in an automobile have been applied. The latency is the actual time for the system to respond. Interrupts are a critical part of the hardware-software interface. With a serial port, it is necessary to quickly process received data, to avoid it being overwritten by more recently received data. Likewise, with brakes there is a constraint on the time the controller has to respond to the external event. Interrupts are also useful in debugging software.

To go beyond the discussion of a generalized abstraction, it is necessary to consider an actual microprocessor. This paper discusses the use of the nod4 soft core microprocessor to introduce the concept of interrupts to undergraduate students. But to strike some kind of balance, nod4 exception handling is fairly generic roughly following the discussion in Tanenenbaum1 and it also borrows concepts from other processors as well. Apart from the implementation, nod4 is classic accumulator based Von Neumann style architecture and as such is similar to many other processors. This implementation is called soft as it is implemented with a Field Programmable Gate Array (FPGA). The FPGA and modern computer aided design tools provide new opportunities in teaching computer architecture. The grand vision is expressed neatly in the motto that the nod4 processor is a simple yet non-trivial processor designed to be a tool for teaching introductory computer architecture principles to undergraduates.

Introduction

From a computer user’s point of view, interrupts simply provide a means for a computer to quickly respond to significant real-world events. From a programmer’s point of view, interrupts provide a means for the hardware to almost magically invoke a subroutine to service a device as necessary, freeing up resources that might otherwise be used for polling. Unlike polling, which is generally suitable for interfacing slow peripherals, interrupts provide a more efficient means to interface with devices. Traps such as the software interrupt instruction (swi) are similar to interrupts and are invoked with the same mechanism. The swi instruction is typically used to implement break points for use in program debugging.

Hill, J. (2008, June), Using An Educational Microprocessor Architecture And Fpga Implementation To Introduce Interrupts Paper presented at 2008 Annual Conference & Exposition, Pittsburgh, Pennsylvania. https://peer.asee.org/4173

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