I am a firmware engineer at Power supply manufactirer and we have roughly 20+ legacy products with the motorola MC68701, MC6800 series processors used. We have exhausted sources of the MC68701 and need to replace it with micr controller that has the same or very similar instruction set. I have been reviewing the datasheets for current production parts for a viable replacement, but could use some help choosing the best match.
The MC68701U4S-1 is the most widely used part in our legacy products. The UV PROM is not used in any of the code any way, so that is not important for the replacement to have non-volatile. All of the code is very simple interfacing with parallel ADC's, DAC's, bus transceivers and then uses SCI (UART) to communicate between master and slave micro controller in the same power supply.
In a perfect world:
The best case scenario is I could take the source code I have now (assembly) and change some register names, memory locations and compile it. Design a small adaptor pcb to adapt from DIP40 to the current layout. I would be curious to seek your opinion on this. Some of these design are used in military applications and the less code changes the better because of the re qualification testing needed.
From the reading I have done so far, the MC68008 seems like a good fit. The instruction set for the MC68008 seems to match up pretty close. I know it is not reccomended for new designs, but we could make a lifetime buy now.
In the past I have used a PIC and completely reverse engineered the entire design, and basically started from scratch and wrote the code with C. This is a very time consuming process and if I can cut that down by using a Freescale product then I would like. After some research it looks like it would save a lot of time and be closer to original design (if not exactly the same).