Benjamin Khan wrote:

Is it possible to use the program flash as RAM for temporary storage? Does any microcontroller support such a feature?

Well, you can't really think of flash as RAM. RAM stands for "random access memory". With RAM, you can read or write to any address at any time. Flash memory is different. Generally speaking, you can only write to an address that has been previous erased, and you have to erase the cells in groups called "blocks". The size of each block depends on the device, and a single device may contains blocks of different sizes. Find a data sheet to learn the details.

Now, if we change your question to, "Is it possible to use the program flash as memory for temporary storage?", the answer is "maybe". It depends on a lot of things. Here are some I have thought of:

• Can the micro execute out of one part of the flash while it erases and/or writes another?
• Are you updating the temporary data often? Flash memory has a fixed limit on how many times you can erase it, and you might eventually exceed this limit if you are making a lot of frequent changes.
• Erasing and writing to the flash memory is slower than writing to RAM. Would that be okay in your application?
• As noted above, to change the contents of one location, you have to erase the entire block that contains that location. Would that be okay in your application?

There may be other considerations that I have not thought of. In order to consider flash for temporary storage, you need to first understand how flash memory works, and then think very carefully about how you are planning to use it.

-- Russ