This page will help you establish a simple test program to determine if your 812A4 board is operational. For your first program, it would be preferrable if you tried this simple program. That will allow you to determine if your 812A4 is operational or not.

Note: While this looks very similar to the test procedure for my other HC12 boards, be warned that the addresses used here are specific to the 68HC812A4.

You should consider picking up a copy of SBASIC for the HC12. It is a simple version of the BASIC language that is free and known to work fairly well. You can find a copy by looking at http://www.seanet.com/~karllunt/sbasic.htm

Hello World

All good computers start with a hello world program. We are going to use a programming language called SBASIC to create, compile, and download a simple program that will determine if the serial port works. There are more complicated tests a little later.

If you don't want to mess around with getting SBASIC right now, you can find the pre-compiled version of this test program in hello12.s19 . The original test file is in hello12.bas

There are a few important things to point out about the above program. Compiling the sbasic program used a set of command line flags that I would like to point out.

The code starts at $F000 (/cF000), this is the start of EEPROM on the 812A4

Variable storage is starting at $0800 (/v0800), this is the default position for RAM.

The Stack has been set to $0C00 (/s0c00), which is the end of RAM. The stack grows down.

I told the SBASIC compiler to output 68HC12 code (/m6812).

This should compile and generate a file called hello12.s19, which contains the object code for the 812A4 board.

Downloading the S19 file

To download your code, you need to use a BDM12 interface pod or equivalent. Here is the instructions for running db12 to download your code.

1. Connect power to the POWER 
2. Connect your BDM12 interface pod to the 812A4 and to your PC's serial port
3. Start db12.exe, which is the debugger.
4. Use the config reset 812A4 command to set the debugger to the correct settings
5. Use the reset command in db12 to stop the target board.
6. Use the 'load' command to load the .S19 file
7. Use the 'reset' command to reset the cpu.
8. Unassemble using the 'u' command. You should see 'real' instructions at the starting point.

At this point, you should have seen output looking something similar to the following. Note that the date of the debugger and some of the other values may be a little different before you issue the load command.

At this point, you will need to connect the 812A4 X1 connector to a PC. If you have a second machine, you can connect it there. Otherwise, you may need to shut down db12.exe.

In either case, you will want to start Hyperterm or some other terminal program. Setup for 19200 on the baud rate. When you have done so (in Hyperterm, after setting the configuration, you may need to 'hang-up' then reconnect), you can press the reset button on the 812A4, and the program should print out Hello World!

Testing the Serial EEPROM

The next test program is written in Imagecraft C www.imagecraft.com/software

If you don't have Imagecraft C, you can just use the .S19 file I am providing.

Source Code:

sermem.h sermem.c memtest.c

Object Code:

I am not going to list the code here, but you are welcome to take a look.

IMPORTANT: Compile so that code is at $F000, RAM is at $0800, stack is at $C00