A computer nightmare

CPU_3A2 module

I needed to have another look at my original CPU_3A3 68HC11F1 module. I was assembling a few of these and needed to test them. Last time I did this, 5 or 6 years ago, I still had a laptop running Windows-98  and a bootloader program that was written about 12 years ago (from memory) using Visual Basic.

The serial communications had always been a bit dodgy  out of Windows as whenever you moved the mouse or Windows decided to do something, the serial flow was often paused briefly. Normally this doesn’t matter, but for the HC11 bootloader, a pause indicates the end of the transfer. You can see how this easily leads to failed transfers.

The original VB based bootloader program supports writing to RAM, EEPROM and the FLASH memory chip of the CPU_3A3 board.

So the problem with testing CPU_3A3 boards now is that I’ve been using Linux almost exclusively for some years and only have one laptop that occasionally boots into Windows-XP. As expected, I discovered that there is no simple way to bootload the HC11 using Linux. There are a few home-brew tools but nothing I cold find that was simple.

So back to Windows-XP to install the original bootloader. Unfortunately it didn’t work; run time errors, the windows “OK” button and instant exit. The thought then was to install Win-95 or Win-98. Long story short… no luck; huge waste of time. Always something in the way preventing a simple solution; hardware, disks, drivers, file transfer, always something wrong.

Installing DOS

Back to DOS

After messing about with a number of computers for more than a day I found an old Basic language bootloader dating back to the 1980’s that should work with DOS and be easy enough to modify to load the required HEX files. Now to find a DOS computer.

I had a computer with Novel DOS-7 installed but the power supply had died and as it’s a small form-factor case I didn’t have the parts on hand to fix it. The only other machine I had with a floppy drive was a spare DEL Optiplex GX-270. Some more messing about and I got DOS installed from the 6 floppies to a 1G partition on the 80G hard drive. Having no network or CD support, I used a compact flash card as a portable hard-drive to transfer other various files over. It’s surprising how quick the DOS commands come back to you; and this is one heck of a fast DOS computer.

Actually too fast… The bootloader program uses loop delays and a single loop can only go to about 32000. I’ve had to modify the program to extend the delays and slow it down.

Original bootloader files: HC11BOOT_1_3 . BUFF_P6_3A.s19

IMO… Windows is a very poor choice for anything even slightly outside of basic computing; browsing, email etc. Especially this technical engineering stuff. We need something that can be made to work in 10 or 15 years time. Nothing proprietary or involving forced upgrades, or locked in any way. 10-15 years ago we didn’t have any choice but to use DOS or what now seems to be a very primitive form of windows; the drivers were a disaster. Most current computer users don’t know how lucky they are.

Update

After many hours of work I finally got the bootloader working well on the DOS machine and tested the boards. I’m even using the machine to edit and assemble; using XT-Gold as a file manager and hub to run other programs from. And Cross-Talk as the comms program.

I tried Minicom on the Linux laptop as a comms monitor but it couldn’t keep up with the HC11 at 19200 baud. The HC11 has a double buffered serial port and there are no gaps between bytes. Minicom couldn’t cope. Cross-Talk on DOS is fine and Terra-Term on Windows is fine. There is still no decent serial comms program for Linux that I can find.

I thought 2 of the flash memory chips were faulty as I couldn’t erase or write them. More time spent experimenting with a couple of spare boards and I wrote a test program to run from RAM to exercise the flash and read out the status info. I found that the chips are write protected.

It’s a internal mechanism that can only be turned off with a suitable external programmer. Lots of web searching discovered that AMD don’t publish details of how it works so I can’t bodge something together. Another perfect example of why you should stay well clear of proprietary and restricted products and information.

Luckily I can get a couple of replacement chips out of Element-14 over night… as soon as they have finished rebuilding their web site.