Static random access memories

There are two general types of RAM, static RAM (SRAM), and dynamic RAM (DRAM). SRAM is based on the flip-flop circuit discussed previously. Two cross-coupled transistors comprise the basic storage unit, a logical 1 if one transistor is on and a logical 0, if the other is on. Two more transistors sense the state, and two more transistors control the access to the storage location, so six transistors are required to store one bit of information. Access time ranges from 10 to 30 ns. The term static refers to the fact that the information remains stored as long as the system is powered. When power is removed, the state of the flip-flops becomes indeterminate hence, data is lost unless stored on the hard drive. Such a memory is called a volatile memory. 

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Typical results obtained for the 256-kbit static random access memories (SRAMs), which were developed for space application by NASD A, are shown in Fig. 15. The SEU cross section increased with LET in a range above a threshold value and reached a constant... 

Fig. 3. Experimental demonstration of one-, two- and three-transistor logic circuits with CNTFETs [41]. Output voltages as a function of the input voltage are given for (A) an inverter, (B) a NOR gate, (C) a static random access memory cell (SRAM) and (D) a ring oscillator.

SRAM The S in SRAM stands for static. Static random access memory doesn t require the refresh signal that DRAM does. The chips are more complex and are thus more expensive. However, they are faster. DRAM access times come in at 80 nanoseconds (ns) or more SRAM has access times of 15 to 20 ns. SRAM is often used for cache memory. 

One type of memory is known as static random access memory (SRAM). It is called static because the information doesn t need a constant update (refresh). SRAM stores information as patterns of transistor ons and offs to represent binary digits. This type of memory is physically bulky and somewhat limited in its capacity. It can generally store only 256Kb (kilobits) per IC. The original PC and XT, as well as some notebook computer systems, use SRAM chips for their memory. 

A. Dynamic Random Access Memory (DRAM) is the type of memory that is expanded when you add memory. Static Random Access Memory (SRAM) is often used for cache memory. See Chapter 2 for more information. 

M. D. Austin et al., 6 nm half-pitch lines and 0.04 mm static random access memory patterns by nanoimprint lithography, Atonofec/moZogy, 16, 1058, 2005. 

Static random-access memory (SRAM) This memory is static because it needs not to be refreshed. It is random access because it can be read and written. 

Dual-inline memory module (DIMM), pioneered by Hitachi, has memory chips mounted on both sides of a PC board (with 168 pins, 84 pins on each side). The DIMM has keying features for 5-, 3.3-, and 2.5-V inputs and for indicating whether it is made with asynchronous DRAMs or flash, static random access memory (SRAM) or DRAM ICs. There is also the SO DIMM or small outline dual in line memory module, which has 72 pins vs. 168 for standard DIMM modules. 

Nonvolatile ferroelectric random access memory (FRAM) devices Dynamic random access memory (DRAM) and static random access memory (SRAM) devices based on semiconductor technology are volatile that is, they wiU lose stored information when the power fails. Nonvolatile devices such as CMOS (complementary metal oxide semiconductors) and EEPROMs (electrically erasable read-only memories) are forbiddingly expensive for mass-produced electronic devices. As described above (see Section 8.3), the magnitude and direction of polarization of a ferroelectric ceramics can be reversed by applying an external electric field, and this method is used by FRAMs to store (or erase) data. As the materials have a nonlinear hysteresis curve, the polarization remains in the same state when the voltage is switched off (i.e., the information originally stored is maintained). In addition, FRAMs may be radiation-hardened for use in harsh environments such as outer space (Scott and Paz de Araujo, 1989). 

Fukuda K, Sekitani T, Zschieschang U et al (2011) A 4 V operation, flexible Braille display using organic transistors, carbon nanotube actuators, and static random-access memory. Adv Fimct Mater 21 4019 027... 

Memory Designs can contain read-only memory (ROM), dynamic random-access memory (DRAM), and static random-access memory (SRAM). In addition, MICON also supports the use of cache memtMies wh cache controller chips exist in the family, such as the Intel 80386/82385 combination. 

Static Random Access Memory (SRAM) sections. Stack, data, sdata, bss, and sbss. For simplicity we refer to SRAM locations as memory words in this paper. 

CMOS flip-flop circuits also form the basis of static random access memories (SRAMs) which store each bit as the state of one of the two transistors in a flip-flop circuit. 

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