If you're not VERY familiar with the Keil product, perhaps you're "shooting yourselves in the foot" by using it. This looks to me like a situation that should, under any circumstances, be handled in ASM and not in 'C' or any other HLL. Once it's in place and proven, you can try reducing the ASM portion of your code. However, if you don't know enough about this architecture to write all the code in ASM, you won't have any better result doing it in 'C'. Whether you use KEIL or anyone else doesn't matter. It's a problem best solved with ASM. If, later on, for maintainability reasons or whatever, you choose to write the code in 'C', that's your choice.


Why go through all this pain? Can't you simply map your CAN controller into the SFR space? There's plenty of room.



First, you have to have an answer to the question, "Why should one use external memory space?" I don't know what benefit you sought by using a "wrapper". If the core you're using has the external address lines defined, and if it executes the MOVX instructions that use those address lines, you should have no difficulty. Since you're using no external memory, I see no advantage in mapping the CAN controller into external memory space. Perhaps you'd like to explain what benefit you see in doing that.

RE