Lab 2

Cross compiling on a host system

Before the Lab

In this lab you will learn to use a host program development system.  It provides support for editing, assembly and downloading of your MC68HC11 programs. Procedurally, you will set up your Axiom board and terminal as usual.

After booting up the Axiom board, an MS-Windows hyper-terminal window should be opened to allow a communication with the HC11 board.  Then, an MS-DOS command box window must be opened to let you edit and assemble your programs.  Once the binary file of your program is complete (in Motorola S-format) it is dumped from the disk file in the DOS host to the Axiom board.  The program may then be run and debugged.  Any changes made in the program at run time (on the Axiom board) must be re-entered in the program file on the host, but when you are done you have a permanent record of your program in machine-readable form.  The on-line assembler also makes it much easier to insert words of code without having to recalculate all of your offsets, etc.

Your first exercise will be to enter, download and run a program you have already written, to familiarize yourself with these techniques.  Review your code for the program that fills page $C100-C1FF with even address values to make sure you understand it and that it works correctly.

You will also be required to perform some other manipulations. One area in which microprocessors exhibit distinct advantages over hard-wired logic systems is in the total flexibility of the tasks that they can execute. Many times control algorithms will require counting of objects or finding the maximum value in a list of data.  Write programs to do the following:

1. A list of numbers (representing, for example, the weights of items coming off of an assembly line) begins at location  $C100.  The end of the list is signified by a “null” byte ($00), indicating an item of 0 weight (no item). Find the total number of items produced.

2. Now write a program to find the maximum value in the list.

3. Quality control requires some degree of uniformity in the finished product. Write a program to find out whether the maximum value in the list is greater than twice the minimum value in the list.

You must make your own list; use one of at least 15 numbers.  These numbers can be entered via the assembler “FCB”  command; see the manual for details.

In order to complete this assignment in a timely fashion, you must write and enter these programs into the host system BEFORE YOU COME TO LAB.  This means in turn that you have some familiarity with the MS-DOS system and the EDIT editor IN ADVANCE (NOTEPAD under Windows also works).  You will not be permitted to enter the lab until your TA has checked that your program is on the DOS system.  This requirement will hold true for all remaining labs.

Assembling your program

The cross-assembler for 68HC11 code is a program called "as11.exe". Separate documentation for this program is available elsewhere in the lab manual. The procedure for assembling your program is as follows:  type "as11 filename.asm" where filename.asm is the program you generated using the editor.  The cross-assembler will do its job, and will either generate error messages or will tell you that it has successfully completed assembly.  In either case, if you have included "l" in your option line (e.g., opt l,s) it generates a list file and send it to the default output device. To be able to store on file use redirection as follows:

C:\> asl1 -lo filename.asm

which will save the listing in a file containing the opcodes and addresses generated (along with error codes, if any).  If assembly is successful, it also generates a file called “filename.s19”, which is the object code in Motorola S-format.  Since S-format is in ASCII, this file may be typed or printed. Check the other assembling options that you can use to generate a cross-reference table, cycle count and a symbol table.

In the Lab

Have the lab TA approve the code that you have generated. The terminal must be connected to the primary port of the Axiom board. In case you suspect baud rate problems, all communication is currently implemented at 9600 baud. Concentrate first on the program that fills a page in memory; it's much simpler and you have a fair chance that it will work.

Downloading to the Axiom board

Once a load module (filename.s19) has been assembled without errors, it's time to test it by running it on the Axiom board. The procedure is simple as follows:

In your windows hyper-terminal select the Transfer->Send  Text File… menu option. Then, specify as File name the filename.s19, and say Open.  This will start transferring the S19 file, and can be verified by the receipt of the BUFFALO prompt (>). You may need to hit the ENTER key once or twice to ensure returning to the monitor.

Once you have successfully loaded and tested your memory fill program, you can appreciate the speed and efficiency of program development when supported by a host system.  Now you are in a position to work on the other programs, which are more challenging, but with such powerful tools should be no trouble at all...

Enter your programs and verify correct operation.  Keep records of the results.  Test your programs with at least two different sets of values in the data lists.

After the Lab

Print listings of your correctly operating programs, which should be liberally commented.  Insert these in a program notebook.  Make notes on any peculiarities of the system you may have noticed.

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