Hc11: Fill & Download for Free

After about half a year, I wrote the code on a Motorola HC11 microcontroller to acquire data from a box used in seismic testing and having a proprietary parallel interface, and store the data in banks of battery backed memory. The HC11 also had a GPIB interface to upload the data to a MS-DOS PC, and a primitive front panel display and control buttons. I also programmed the PC to upload the data from the GPIB interface and store it in spreadsheet compatible data files.

First of all, I should state that my favorite Motorola processor was the 6809, which was a microprocessor, not a microcontroller. I like programming in assembly language, and the 6809 was a dream to program. It had ten indexed addressing modes, which I talk about here.So about seven years after the 6809, Motorola came out with the 68HC11 micrcontroller. Like the 6809, it had added a second index register (IY) and D register pair. But the second stack pointer (U) was missing. It was handy for writing multi-tasking operating systems. And the instruction set was hobbled — fewer addressing modes, and every instruction referencing the IY register added an instruction prefix byte (0x18).So from an assembly language standpoint, I didn’t like the HC11 anywhere near as much as the 6809. I did a couple of embedded projects with the HC11, but they were almost all in C, so it didn’t really matter except for the larger code size due to the instructions using IY.Most of this was fixed with the successor to the HC11, the 68HC12. Unlike the 6809 and HC11, which were both 8-bit internally with some 16-bit registers, the HC12 was a 16-bit microcontroller with 16-bit internal data paths.Except for the lack of the second stack pointer (U), the HC12 is much more like the 6809. Gone is the penalty for using the second index register Y. It had most of the missing indexed addressing modes, and even new addressing modes that were not even on the 6809, such as Accumulator Offset Indexed Addressing and Accumulator D Indirect Indexed Addressing. It even had some fuzzy logic instructions (MEM, REVx, and WAVx).I’ve never had the opportunity to do a project with the 68HC12 but I think I would have enjoyed doing so. It still lives on, as the MC9S12 family from NXP which is still available.

Yes, these devices have real value. Note that the simple PCBs that allow a designer or student to jump right in to coding and experimenting are a HUGE advantage. The old days of designing and debugging PC boards were a rite of passage but in todays world getting learners right into battle is a real plus. The PCB design and debugging plus ROM programmers and UV erasers were a big problem for people interested in starting. As a designer of products with long lifetimes I always want to specify the silicon parts and install them on my own PCBs for the actual product. Little development board assemblies come and go at a rapid pace and make product support a real headache. I have seen development boards (Motorola HC11) designed into products where the designer felt that he or she did not want to deal with a new PCB design. It cost that company about 10k$ per year to not make their own PCB. I would say that if you want to design little demo boards into small use projects in a business setting such as test equipment, then buy a couple of dozen to keep for backups and continue to buy new ones for use as long as they are available to keep the backups as long as possible.