Flash and EEPROM

Flash is the full name of Flash EEPROM, but it is different from the conventional EEPROM operation method

Flash and EEPROM The biggest difference is the flash by sector operation, EEPROM operation by Byte, the two addressing methods are different, the structure of the storage unit is also different, flash circuit structure is simpler, the same capacity for the chip area is small, the cost is naturally lower than EEPROM, Therefore, it is suitable for use as program memory, and EEPROM is more used as nonvolatile data memory. Of course, using Flash to do the data memory, but the operation is more troublesome than EEPROM, so more "humanized" MCU design will be integrated flash and EEPROM two nonvolatile memory, and inexpensive design often only flash, the early electro-writable MCU is the EEPRM structure, It is now largely discontinued.

As for that "chief engineer" said words if not Zhang a knife in the wrong words, that is even the basic concept is wrong, can only say that "chief engineer" not only do not understand the chip design, even the basic structure of the MCU system is not mastered. In the chip of the circuit, Flash and EEPROM not only the circuit, address space is also different, operating methods and instructions are also different, regardless of the von Neumann structure or the Harvard structure is the case. Technically, the program memory and non-volatile data memory can be used only FALSH structure or EEPROM structure, even with "flexible" technical means in the program store Simulation "data store", but even so, the concept is still different, this is the basic common sense problem.

No rigorous work spirit, can not become a true technical master.

EEPROM: Electric erasable Programmable read-only memory, flash operation characteristics fully conform to the definition of EEPROM, is an EEPROM is undoubtedly, the first flash launched its data manual is also clearly marked as EEPROM, and now most flash manuals are so marked, The relationship between the two is "White Horse" and "horse". As for why the industry to distinguish between the two, the main reason is the Flash eeprom operation method and the traditional EEPROM is very different, the secondary reason is for the brevity of language, non-official documents and the Flash EEPROM in the spoken word is abbreviated as Flash, here to emphasize the white horse "white" attribute instead of its "horse" attribute to differentiate between flash and traditional EEPROM.

Flash is characterized by a simple structure, the same process and the same crystal area can get higher capacity and large data volume of operation faster, but the disadvantage is the operation process trouble, especially in the small amount of data repeatedly rewrite, so in the MCU flash structure suitable for the program memory without frequent rewriting.

In many applications, the need to frequently rewrite some small amounts of data and the need to power off non-volatile, the traditional structure of the EEPROM is very suitable, so many MCU internal design of the two EEPROM structure, flash and traditional in order to obtain the cost and function of the balance, which greatly facilitates the user. With the popularity of ISPs, IAP, especially in the MCU system where the program stores the address space and the data storage address space, more and more MCUs are producing commercial support IAP program memory to simulate the EEPROM corresponding data memory, which is a workaround for low cost non-volatile data memory. In order to obtain the "equivalent" of the dual-EEPROM process in the commercial propaganda, many use Flash program memory "simulation" (note that the technical concept is not true analog) EEPROM data memory manufacturers have claimed that their products are with EEPROM, strictly speaking, this is very not rigorous, But businessmen have the purpose and method of businessmen, using flash "simulation" EEPROM can gain greater commercial interests, so in fact, the technical concept of confusion is the initiator of them.

From the cost of speaking, with flash "simulation" EEPROM is a bargain, but no one will do, then the "Chief engineer" and the upstairs of a netizen said that the use of EEPROM simulation flash is what? This may be in some program storage space and data storage space on a continuous MCU. Such MCUs, especially low-end MCUs with little storage capacity, still use EEPROM as nonvolatile memory, which is less costly than the dual-process design of flash and traditional eeprom, but this phenomenon is limited to small capacity. Because of the popularity of Flash technology, now many businessmen and not rigorous technical staff will be called Flash Program memory, for those who only use the traditional EEPROM process MCU, they superficial understanding, so the wrong EEPROM program memory called "Analog Flash", The root cause is that they don't understand that Flash is just a memory structure, not a memory, and the wrong premise naturally leads to the wrong conclusion. Commercially speaking, the use of EEPROM simulation Flash is no one really to do stupid behavior, which is contrary to the principle of business pursuit of the best interests, technically not feasible, and for technical personnel, especially the IC industry, "chief engineer" If you say that he or she does not know the relevant technical details, Either very not rigorous, this is not in line with the "Chief engineer" identity. The essence of the problem is that Flash is a type of memory rather than a program memory in the MCU, even though the MCU's program memory is flash, but its inverse proposition is not true.

Write this article, on the one hand is to clarify the technical concept, on the other hand is not to make the wrong statement fraught, technology also need rigorous scientific spirit.

28 Series is the earliest eeprom,28f is the earliest flash, and even the word flash is Intel in 1980S to promote its 28F series from the "Advertising name", take its meaning "fast", only that. Flash of the year was not larger than the traditional EEPROM capacity only slightly higher than the capacity starting point. As for the current manual is not important, do not want to "more sticks" words, to see if there is no "electric erasable" memory, at least I opened the SST Flash manual is written very clearly, but these are basically meaningless fur, typical horse theory.

As for the AVR address continuous problem is I casually mistake, should refer to the 68HC series, but even so, even if I have not used any MCU, including the AVR has nothing to do with the nature of Flash.

Flash and EEPROM