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| en:multiasm:cs:chapter_3_6 [2025/12/04 12:38] – [Flash EEPROM] ktokarz | en:multiasm:cs:chapter_3_6 [2025/12/04 12:53] (current) – ktokarz |
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| ===== Flash EEPROM ===== | ===== Flash EEPROM ===== |
| Flash EEPROM is a version of non-volatile memory that is similar to EEPROM. Whilst in the EEPROM, a single byte can be erased and reprogrammed, in the Flash version, erasing is possible in larger blocks. This reduces the area occupied by the memory, making it possible to create denser memories with larger capacity. Flash memories can be realised as part of a larger chip, making it possible to design microcontrollers with built-in reprogrammable memory for the firmware. This enables firmware updates without the need for any additional tools or removing the processor from the operating device. It also enables remote updates of the firmware. | Flash EEPROM is a type of non-volatile memory that is similar to EEPROM. Whilst in the EEPROM, a single byte can be erased and reprogrammed, in the Flash version, erasing is possible in larger blocks. This reduces the area occupied by the memory, making it possible to create denser memories with larger capacity. Flash memories can be realised as part of a larger chip, making it possible to design microcontrollers with built-in reprogrammable memory for the firmware. This enables firmware updates without the need for any additional tools or removing the processor from the operating device. It also allows remote firmware updates. |
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| ===== FRAM ===== | ===== FRAM ===== |
| FRAM - Ferroelectric Random Access Memory is a type of memory where the information is stored with the effect of a change of polarity of ferroelectric material. The main advantage is that the power efficiency, access time, and density are comparable to DRAM, but without the need for refreshing and with data retention while the power is off. The main drawback is the price, which limits the popularity of FRAM applications. Currently, due to their high reliability, FRAMs are used mainly in specialised applications like data loggers, medical equipment, and automotive "black boxes". | FRAM - Ferroelectric Random Access Memory is a type of memory where the information is stored with the effect of a change of polarity of ferroelectric material. The main advantage is that the power efficiency, access time, and density are comparable to DRAM, but without the need for refreshing and with data retention while the power is off. The main drawback is the price, which limits the popularity of FRAM applications. Currently, due to their high reliability, FRAMs are mainly used in specialised applications like data loggers, medical equipment, and automotive "black boxes". |
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| ===== Volatile memories ===== | ===== Volatile memories ===== |
| Volatile memories are used for temporal data storage while the computer system is running. Their content is lost after the power is off. Their main application is to store the data while processed by the program. Their main applications are operational memory (known as RAM), cache memory, and data buffers. | Volatile memory is used for temporal data storage while the computer system is running. Their content is lost after the power is off. Their main application is to store the data while the program processes it. Their main applications are operational memory (known as RAM), cache memory, and data buffers. |
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| ===== SRAM ===== | ===== SRAM ===== |
| SRAM - Static Random Access Memory is the memory used as operational memory in smaller computer systems and as the cache memory in bigger machines. Its main benefit is very high operational speed. The access time can be as short as a few nanoseconds, making it the first choice when speed is required: in cache memory or as the processor's registers. The drawbacks are the area and power consumption. Every bit of static memory is implemented as a flip-flop and composed of six transistors. Due to its construction, the flip-flop always consumes some power. That is the reason why the capacity of SRAM memory is usually limited to a few hundred kilobytes, up to a few megabytes. | SRAM - Static Random Access Memory is the memory used as operational memory in smaller computer systems and as cache memory in larger machines. Its main benefit is very high operational speed. The access time can be as short as a few nanoseconds, making it the first choice when speed is required: in cache memory or as the processor's registers. The drawbacks are the area and power consumption. Every bit of static memory is implemented as a flip-flop and composed of six transistors. Due to its construction, the flip-flop always consumes some power. That is the reason why the capacity of SRAM memory is usually limited to a few hundred kilobytes, up to a few megabytes. |
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| ===== DRAM ===== | ===== DRAM ===== |
| DRAM - Dynamic Random Access Memory is the memory used as operational memory in bigger computer systems. Its main benefit is very high density. The information is stored as a charge in a capacitance created under the MOSFET transistor. Because every bit is implemented as a single transistor, it is possible to implement a few gigabytes in a small area. Another benefit is the reduced power required to store the data in comparison to static memory. But there are also drawbacks. DRAM memory is slower than SRAM. The addressing method and the complex internal construction prolong the access time. Additionally, because the capacitors which store the data discharge in a short time, DRAM memory requires refreshing, typically 16 times per second; it is done automatically by the memory chip, but additionally slows the access time. | DRAM - Dynamic Random Access Memory is the memory used as operational memory in bigger computer systems. Its main benefit is very high density. The information is stored as a charge in a capacitance created under the MOSFET transistor. Because every bit is implemented as a single transistor, it is possible to implement a few gigabytes in a small area. Another benefit is the reduced power required to store the data in comparison to static memory. But there are also drawbacks. DRAM memory is slower than SRAM. The addressing method and the complex internal construction prolong the access time. Additionally, because the capacitors which store the data discharge in a short time, DRAM memory requires refreshing, typically 16 times per second; it is done automatically by the memory chip, but additionally slows the access time. |
