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Innovative Lab Station Using the Freescale ‘HCS12 Microcontroller and Dragon Development Board

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Abstract

The Freescale ‘HCS12 sixteen-bit microcontroller is a popular vehicle for teaching introductory microcomputer system design. Freescale’s Dragon development board is often the foundation for lab station implementations. However, the Dragon board usually is used with a dedicated personal computer at each station, which is expensive and which leads to a cluttered lab environment. Individual personal computers are unnecessary, and are overkill for the needs of the lab. What is required is a central computing facility on which students can create, edit, and assemble assembly language programs, and from which students can download the resulting object files into the Dragon boards at their stations. This paper details a lab environment that uses a single personal computer running the multi-user LINUX operating system, serving as a host for all lab stations in the microcomputer design lab. This environment removes the clutter and expense involved with personal computers at every station, but requires some enhancements to the Dragon board to allow the lab stations to function as independent terminals on the LINUX system.

To work as independent stations on the LINUX system, each station must include an alphanumeric keyboard and an alphanumeric display to provide capability to interact with the host computer as a terminal for creating, editing, and assembling source code. The design of the lab station presented here includes an alphanumeric matrix keyboard, scanned using the n-key rollover algorithm through two of the eight-bit input/output ports on the Dragon board. The lab station design also includes an alphanumeric display, showing thirteen rows of thirty-two characters each on a standard, low-cost television monitor. The composite video for the television display is generated using a Serial Peripheral Interface (SPI) on the ‘HCS12 microcontroller, and requires only a few external passive components added to the Dragon board.

This paper presents the design of this innovative ‘HCS12 Dragon-based lab station, and discusses some applications in the lab environment.

Background

The Freescale ‘HCS12 sixteen-bit microcontroller is a descendent of the very popular Motorola MC68HC11 8-bit microcontroller. The instruction set of the ‘HCS12 is a full superset of the instruction set of the MC68HC11, so all programming experience that users have with the MC68HC11 is directly applicable for writing programs on the ‘HCS12. However, memory addresses and peripheral device addresses are different in the ‘HCS12 processor, and in some cases, the internal peripheral devices operate slightly differently from those in the predecessor processor, so some effort must be employed to adapt to the ‘HCS12. However, the ‘HCS12 offers significant enhancement of capabilities through an expanded and more powerful

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Carroll, C. (2008, June), Innovative Lab Station Using The Freescale 'hcs12 Microcontroller And Dragon Development Board Paper presented at 2008 Annual Conference & Exposition, Pittsburgh, Pennsylvania. 10.18260/1-2--3709