HC-11 Evaluation Board
Wichit Sirichote, kswichit@kmitl.ac.th

Build a low-cost learning board, HC-11EVB for studying the MOTOROLA 68HC11A1 Assembly and C language programing.Downloadable Buffalo V3.4 through the use of Randy's S19 Downloader.


Introduction

After reading theMobile Robots Book,written by Joseph L. Jones and Anita M. Flynn, and get the Interactive-Cfile from ftp://cher.media.mit.edu,I found a very nice S19 downloader written by Randy Sargent. I startedto download the pcode to my HC-11 board, and run Interactive C. No problemwith my board, it works very nice. Then I got the idea for the Buffalomonitor, to use Randy's Downloader writes the S19 file of the Buffalo withspecial boothrap mode. After changing to expanded mode, press reset, thebuffalo prompt appeared. It also works even the circuit was very simple.I thought, I should provide the page for making the board for studyingAssembly and C first, and another page, with additional sensor board, forRug Warrior Robot experiment. The materials herein is for beginners topractice build the microcontroller by themselves.

Hardware

A circuit diagram of the HC-11 EVB is depicted in Figure 1. MODA and MODBpin can be used to configure four operating modes, i.e., special boothrap,special test, expanded and single chip modes. To use with Buffalo monitor,we use only two modes, special boothrap with both pin low for downloadingthe Buffalo and the expanded mode with both pin logic high for experimentingunder Buffalo. A 32kB SRAM 62256 uses 15 lines address, A0-A14, while A15and E pins connect NAND gate, 74HC00, to CE pin. This makes the addressspace of the SRAM to be 8000H-FFFFH, i.e., A15 must be '1' to enable 62256.The Latch 74HCT373 provides A0-A7 to the SRAM. Carefully see the connectionfor input data and the output latch, if you find 74HC573, the connectionmay easier. The RS232 Level converter uses DS275 or MAX232, whichever youfind. ULN2003 is used for LED driving and also for small DC motor experimentingwith PWM. The i/o port left for experiment are port E analog input, portA and port D.
 
FigureFigure 1: Circuit Diagram of the HC-11 Evaluation Board
 

Figure 2:  PLCC Socket for UniversalPCB Soldering

Software

Randy'S19 Downloader, dl.exe,is used for downloading the Buf34.s19into the HC-11'32kb SRAM, $E000-$FFFF. The downloader works well underDOS mode. To download Buffalo, first, put the 68HC11 to bootstrap loading,by making MODA and MODB to GND, then invoked;

c:/buffalo/dlbuf34<

After success downloading, change operation mode to normal expandedmode, i.e., left MODA and MODB high. Run any terminal emulation programwith 9600 8n1, that all. Figure 4 shows example of Buffalo monitor functions.Study also the buffalo source code, Buf34.asm, and use of As11.exe,the 68HC11 Assembler, for experimenting with Assembly programming. SeeAS11reference manual for details.

 
updated, 6 October 2542