The difference between SRAM and DRAM

Random access memory (RAM) is divided into static random access memory (Static random access memory-sram) and Dynamic random access memory (Memory-dram).

one, static random access memory (SRAM)

Static random access memory is aRandom access memoryone of them. The so-called "static" refers to the memory as long as it remainsPower on, the data stored in it can be kept constant. Relative,dynamic random access memorythe data stored in (DRAM) needs to be updated periodically. When the power supply is stopped, the data stored in the SRAM will disappear (known as volatile memory), which can be stored after a power outage.ROMorFlash Memoryis different. SRAM is composed of storage matrix, address decoder and read/write control circuit, the capacity expansion has two aspects: the expansion of bits in parallel with the chip, the expansion of the number of words can be used in addition to the decoder chip select input Terminal . Each bit in the SRAM is stored in Two cross-coupled inverter consisting of 4 Fet (M1, M2, M3, M4). The other two Fet (M5, M6) is a control switch that stores the basic unit to a bit line for reading and writing, as shown in 1.

Figure 1

In addition to the 6-tube SRAM, the other SRAM also has 8 tubes, 10 tubes, and even each bit uses more transistor implementations. This can be used to implement read-write access to a multiport port (port), such as video memory or a memory base unit using less than 6 transistors is possible, such as 3 tubes Even single tube, but single tube storage unit is dram

S ram is more expensive than DRAM, but faster and very low power consumption (especially in idle state). SRAM is therefore preferred for bandwidth requirements, or low power requirements, or both. SRAM is much easier to control than DRAM, and more random to access. Due to the complex internal structure, SRAM occupies a larger area than DRAM,

the SRAM power consumption depends on its frequency of access. If SRAM is accessed at high frequencies, its power consumption is higher than DRAM. Some SRAM consumes up to a few watts at full bandwidth. On the other hand, if the microprocessor is used for a moderate clock frequency, the power dissipation will be very small, and the power dissipation can be negligible in idle state-several micro-watt levels. SRAM is a more common application as a microcontroller RAM or cache (32bytes to 128kb)

second, dynamic random access memory (DRAM)

Dynamic random access memory is a kind of semiconductor memory, the main principle of action is to usecapacitanceInternal Storagechargeto represent a binary bit.(bit) is 1 or 0. Because the capacitance in the reality of the phenomenon of leakage, resulting in insufficient potential for memory loss, so unless the capacitance is often periodically charged, it will not ensure that the memory lasts. This is called "dynamic" memory because of the characteristics that require timed refreshes. In contrast, "Static" Memory (SRAMas long as the data is stored, the memory will not be lost even if it is not refreshed. compared to SRAM, the advantage of DRAM is its simple structure--every bit of data requires only one capacitor and one transistorto deal with. dram usually takes a capacitor and a transistor to form a two-dimensional matrix of a cell, Figure 2 shows a 4x4 matrix, and modern dram is usually long and wide in thousands of. In contrast, the last bit in SRAM typically requires six transistors. For this reason, DRAM has a very high density, with a higher capacity per unit volume and therefore lower cost. DRAM also has drawbacks, and DRAM also has the disadvantage of slower access and greater power consumption. with most of theRandom access memory(RAM), since the presence of data in DRAM can quickly disappear after the power cut off, it belongs to a volatile memory device.

Figure 2

The difference between SRAM and DRAM