ANSWER: Not to Dram.

Truth is, RAM requirements are USUALLY excessively selected in design specifications. Seldom does anyone need the RAM they want. This is why the 8051 works well in so many designs.

I used a lot of Z80 family early in my career and was never a fan of DRAM. The only time it made sense to me was in the standard 64Kx8 requirement of CP/M class machines. For real-time controllers, its just asking for trouble in my opinion. You can do it - yes. I submit there is usually no good reason to do so.

I see external SRAM as only needed for a communications buffer for external FLASH storage. Any automata needs can usually be handled in realtime so you don't need to buffer for that. Unless the device is doing message analysis of a collected cache of recent messages, I can't think of why you'd need much SRAM. Most things you want to store, FLASH and EEPROM would be better. SRAM is basically short-term Cache.

However, most people program in a way that makes excessive SRAM needed. I agree about that. How may people look at RAM reuse between tasks and bother to look for where it is feasible? If you work with 8051s... its something you better start to think about *IF* you are designing for profit.

-Jay C. Box