EEPROM and Flash differences

EEPROM does not erase to write data directly

Power-down needs to be protected and in the course of the program needs to modify a small number of parameters saved in the EEPROM, the number of erase more than flash, Flash used to do programs and some power-down protection and no need to modify the data.

Flash memory refers to "flash", the so-called "flash", it is also a non-volatile memory, belongs to the improvement of the EEPROM products. Its greatest feature is that it must be erased by block (each block is variable in size, different manufacturers have different specifications), and the EEPROM can erase only one byte at a time (byte). At present, "flash" is widely used in the PC motherboard, used to save the BIOS program, easy to upgrade the program. Another area of application is used as a substitute for hard drives, with the advantages of seismic, fast, noise-free, low power consumption, but it is inappropriate to replace RAM, because RAM needs to be able to be rewritten in bytes, and Flash ROM does not.

Flash is the full name of the 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 data storage, but the operation is more troublesome than EEPROM, so more "humanized" MCU design will integrate FLASH and EEPROM two nonvolatile memory, and inexpensive design often only flash,eeprom in the run can be modified,     While Flash cannot be modified at runtime, EEPROM can store some modified parameters, flash stored program code and no need to modify the data. The so-called Flash is used to describe the entire storage unit content can be erased at once. Therefore, in theory, any memory with such characteristics can be called flash memory. E2prom inside also divided Ff-eeprom and Flash EEPROM. Now everyone is talking about flash memory is actually divided into two categories, one is floating Gate device, a class is charge trapping device. The classification standard here is mainly the difference between the program and the erase mechanism.

Add:

A: Flash and E2prom

1: The same point is that both can power down the storage data

2: Difference:

1) Flash by sector operation, EEPROM operation by byte

2) long flash write time, short EEPROM write time

3) Less flash erase (10,000 times), more EEPROM (1 million times)

4) Flash circuit structure is simple, low cost, EEPROM process complex, high cost

Second: The MCU data memory can not be used flash, because:

1:flash has a certain number of erase, write times, the average single-chip flash erase write times the nominal value is 10,000 times.

It takes a long time for 2:flash to write to the data, which requires about 4-6ms. and write Flash need to add 9V of high pressure, trouble.

Three: As for the e2prom, can be used as data memory, but monolithic microcomputer such as atmega128 generally use RAM as the data memory, because the E2PRM process is complex, high cost, suitable for storing the data of power-down protection, This type of data often does not need to be stored too much. So the general SCM is not in the internal integration of e2prom, when needed, you can let a single-chip computer plug 24C01 A class of serial e2prom.