EPROM , EEPROM , SRAM , DRAM

[Ankster]

computer memory wikipedia

hi ,
i want to know how do these things actually work . I searched on google
for that but could find any satisfactory web-site . I actually want to know
how a read , write , erasure operation is done in these memory packages.

Can somebody help me doing that ....


Thanx
Ankur

 

[bobcat1]

how to interface 27c16 with 8051

Hi
Search for the following :\

1) EPROM - Electrical programming read only memory

2) EPROM - Electrical erase and programming read only memory

3) SRAM - static Random access memory


4) DRAM - Dynamic Random access memory


All the best




BObi

 

[woodyplum]

search in any basic circuit book, you can find the answer. EPRON are using the electron in gate oxiside. sram are using transistor structure(commanly 6) while dram using Cap.

 

[mimomod]

Hi Ankster,

see wikipedia!

https://en.wikipedia.org/wiki/Semiconductors
https://en.wikipedia.org/wiki/EPROM
https://en.wikipedia.org/wiki/EEPROM
https://en.wikipedia.org/wiki/Static_random_access_memory
https://en.wikipedia.org/wiki/Dynamic_random_access_memory

best

 

[badri_s255]

SRAM contains normally 6 transistors
DRAM contains 1 transistor/i capacitor cell
Because of its less area DRAM cell is preffered as main memory

BUT SRAM is faster than DRAM and has low power dissipation

 

[BeeBop]

Hi Ankster,
Well, first off EPROM is Errasable Progarmable Read Only Memory, you need a UV erraser to erase these. They are the ones with the small quartz window on top.
EEPROM is Electrically Errasable Progarmable Read Only Memory, These can be erased and written to with a voltage, and do not require the UV eraser.
SRAM is Static Random Access Memory, you write to it once.
DRAM is Dynamic Random Access Memory, you need to write to it constantly to keep it programmed.

Each type of memory is available in several different interfaces: parallel, SPI (serial perifferal interface) and I2C (inter chip interface.)

The parallel parts reqire a line for each data bit, and any number of address lines, depending on the size of the memory array.

The serial parts require fewer lines. I2C usually can be done with two lines (depending on how much memory you are using,) and the SPI with three lines, again, depending on how much memory.

I hope I have anwered your question, but if there is anything else, just post. BTW, what is your application?

Best wishes,
Robert

 

[nopodige]

HI.....
i hope this links would be helpful for u ,,,,,,

1) EPROM and EEPROM
https://www.pcguide.com/ref/ram/types.htm
2) SRAM
https://www.pcguide.com/ref/ram/typesSRAM-c.html
3)DRAM
https://www.pcguide.com/ref/ram/typesDRAM-c.html

i hope u will be satisfied with the explaination given in this link.....

have a nice day

 

[salma ali bakr]

in any datasheet, u will find more info about write and read signals...
u just have to know the basics of each type...to be able to know which to use and where

good luck
Salma

 

[abid_ms]

Here are the clear Defs:

1. DRAM: Dynamic Random Access Memory:
The data will be sotred in any part of this memory and will not be monitored till the need exists. DRAM requires periodic refreshments of the memory blocks. Once the power is off all the data will be errased.

2. SRAM: Static RAM.
This is a high speed RAM compared with DRAM. It requires more silicon area. Data access is fast in this. No periodic refreshments needed in this case.

3. SDRAM: Synchronous DRAM.
This is also an SRAM but will synchronizes with the main processor clock and do the data accessing according to the CPU clock you are using. This is normally used in high-end embedded applications for meeting real-time deadlines.

EPROM and EEPROM are self explonatory by the definations it self. Both are ROMs. The formar is non-volatile whilist the later is volatile.

I think this ends all your doubts.

regds..,
Abid.

 

[mmike]

An EPROM, or erasable programmable read-only memory, is a type of computer memory chip that retains its data when its power supply is switched off. In other words, it is non-volatile. It is an array of floating gate transistors individually programmed by an electronic device that supplies higher voltages than those normally used in electronic circuits. Once programmed, an EPROM can be erased only by exposing it to strong ultraviolet light. EPROMs are easily recognizable by the transparent window in the top of the package, through which the silicon chip can be seen, and which emits UV light during erasing.
A 32KB (256Kbit) EPROM.
Enlarge
A 32KB (256Kbit) EPROM.

As the quartz window is expensive to make, OTP (one-time programmable) chips were introduced; the only difference is that the EPROM chip is packed in an opaque package, so it can not be erased after programming. OTP versions are manufactured for both EPROMs themselves and EPROM-based microcontrollers. However, OTP EPROM (whether separate or part of a larger chip) is being increasingly replaced by EEPROM for small amounts where the cell cost isn't too important and flash for larger amounts.

A programmed EPROM retains its data for about ten to twenty years and can be read an unlimited number of times. The erasing window must be kept covered with a foil label to prevent accidental erasure by sunlight. Old PC BIOS chips were often EPROMs, and the erasing window was often covered with a label containing the BIOS publisher's name, the BIOS revision, and a copyright notice.

Some microcontrollers, often those from before the era of EEPROMs and flash memory, use EPROM to store their program. This is not very useful for development, as using one-time programmable devices would be horribly wasteful for debugging and windowed versions are expensive. Leaving the die of such a chip exposed to light can also change behavior in ways that may be disastrous when moving from a windowed part used for development to a non-windowed part for production. For example a device may power up with data memory random with the die covered but with it in a predictable state with the die exposed to light.

The EPROM was invented by engineer Dov Frohman.
This 8749 Microcontroller stores its program in internal EPROM.
Enlarge
This 8749 Microcontroller stores its program in internal EPROM.

EPROMs come in several sizes both in physical packaging as well and storage capacity
EPROM Type Size — bits Size — bytes Length (hex) Last address (hex)
1702, 1702A 2 Kibit 256 100 000FF
2704 4 Kibit 512 200 001FF
2708 8 Kibit 1 KiB 400 003FF
2716, 27C16 16 Kibit 2 KiB 800 007FF
2732, 27C32 32 Kibit 4 KiB 1000 00FFF
2764, 27C64 64 Kibit 8 KiB 2000 01FFF
27128, 27C128 128 Kibit 16 KiB 4000 03FFF
27256, 27C256 256 Kibit 32 KiB 8000 07FFF
27512, 27C512 512 Kibit 64 KiB 10000 0FFFF
27C010, 27C100 1 Mibit 128 KiB 20000 1FFFF
27C020 2 Mibit 256 KiB 40000 3FFFF
27C040 4 Mibit 512 KiB 80000 7FFFF
27C080 8 Mibit 1 MiB 100000 FFFFF


(also called an E2PROM) or Electrically Erasable Programmable Read-Only Memory, is a non-volatile storage chip used in computers and other devices to store small amounts of volatile (configuration) data. When larger amounts of more static data are to be stored (such as in USB flash drives) other memory types like flash memory are more economic. SEEPROM, meaning Serial EEPROM, is an EEPROM chip that uses a serial interface to the circuit board.


Random access memory
From Wikipedia, the free encyclopedia
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"RAM" redirects here. For other uses of the acronym, see Ram.

A four-megabyte RAM card for the VAX 8600 computer (circa 1986). The RAM chips are located in the rectangular areas to the left and right.
Enlarge
A four-megabyte RAM card for the VAX 8600 computer (circa 1986). The RAM chips are located in the rectangular areas to the left and right.

Random-access memory (usually known by its acronym, RAM) refers to data storage formats and equipment that allow the stored data to be accessed in any order — that is, at random, not just in sequence. In contrast, other types of memory devices (such as magnetic tapes, disks, and drums) can access data on the storage medium only in a predetermined order due to constraints in their mechanical design.

Generally, RAM in a computer is considered main memory (or primary storage): the working area used for displaying and manipulating data. This type of RAM is usually in the form of integrated circuits (IC). These are commonly called memory sticks or RAM sticks because they are manufactured as small circuit boards with plastic packaging and are about the size of a few sticks of gum. Most personal computers have slots for adding and replacing memory chips.

RAM is typically erased when a computer is shut down, though some RAM chips maintain data indefinitely without electrical power. Technically, RAM devices are not limited to memory chips, and random-access memory as a storage format is not limited to use as working memory. In a broad sense, modern storage devices for long-term or secondary storage, including magnetic media and laser-readable CDs and DVDs, are forms of random-access memory.
Look up RAM, random access memory in Wiktionary, the free dictionary.

Most RAM can be both written to and read from, so "RAM" is often used interchangeably with "read-write memory." In this sense, RAM is the opposite of read-only memory (ROM). Strictly speaking, however, "RAM" and "ROM" are not mutually exclusive designations because "RAM" refers only to the method of accessing stored data, not whether data can be written.


Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor. As real-world capacitors are not ideal and hence leak electrons, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory. Its advantage over SRAM is its structural simplicity: only one transistor and a capacitor are required per bit, compared to six transistors in SRAM. This allows DRAM to reach very high density. Since DRAM loses its data when the power supply is removed, it is in the class of

 

[basemgergawy]

In the sence of electonic devices

1) EPROM - Electrical programming read only memory
It's implemented using MOS transistor for each bit. But the MOS transistor has an extra feature which is called "floating gate transistor" which is simplly a normal MOS transistor with a piece of metal embedded inside the oxide, this metal is surrounded by charges and hold this charges. By this way the transistor is permanentlly ON or OFF depending on floating gate charge.
**broken link removed**
An ultraviolet beam of light with certain wavelength can relase the charge and the memory is erased


2) EEPROM - Electrical erase and programming read only memory
Exactlly as EPROM but to erase the memory the floating gate is disharged by electrical signal to remove the charges surrounding the floating gate


3) SRAM - static Random access memory
A memeory but when the supply voltage is removed, it loss it's stored data. It's implemented using D-type flip flop for each bit. The D Flip Flop has input , output, and clock pulse input. The operation of D F.F as follow
* when clock pulse is logic 1, then the output equals the input
* When clock pulse is logic 0, then the output equals the previous input and dosn't change even if the input is changed
But the D-FF needs a large area on the integrated circuit to be implemented so it cann't be used in large memory size


4) DRAM - Dynamic Random access memory
To store voltage in electrical circuit, you need a capacitor. The same thing in RAM. But implementing capacitors on IC need very very large areas. So insted of using capacitors we use varactors which is special type of diodes and has the same characteristics of capacitors. So each bit can be stored using one varactor. The problem with varactors is the leakage of the charge in small time (milliseconds) so the DRAM needs refreshment cycle. In the refreshment cycle all capacitors "varactors" are sensed then recharged with the provious charge to keep the voltage on each varactor constant. The refreshment cycle needs extra and sophisticated circuits.But DRAM can implement very large size of memory on the IC




I hope that my article helped you