(EPROM). The device is organized into 64K words by. 8 bits (64K bytes). Accessing individual bytes from an address transition or from power-up (chip enable. DESCRIPTION. The M is a , bit UV erasable and electrically programmable memory EPROM. It is organized as 65, words by 8 bits. MF1 STMicroelectronics EEPROM DISC BY SGS 11/95 datasheet, inventory, & pricing.
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Archived PDF from the original on To erase the data stored in the array of transistors, ultraviolet light is directed onto the die. Digital Design and Fabrication.
To retrieve data from the EPROM, the address represented by the values at the address pins of the EPROM is decoded and used to connect one word usually an 8-bit byte eeprkm storage to the output buffer amplifiers.
EPROMs had a limited but large number of erase cycles; the silicon dioxide around the gates would accumulate damage from each cycle, making the chip unreliable after several thousand cycles.
This creates an avalanche discharge of electrons, which have enough energy to pass through the deprom oxide layer and accumulate on the gate electrode. Even dust inside the package can prevent some cells from being erased. The switching state of the field-effect transistor is controlled by the voltage on the control gate of the transistor.
Initially, it was thought that the EPROM would be too expensive for mass production use and that it would be confined to development only. Shining ultraviolet light on any part of an unpackaged device causes a photocurrent to flow from the floating gate back to the silicon substrate, thereby discharging the gate to its initial, uncharged condition photoelectric effect. Storing ewprom in the memory requires selecting a given address and applying a higher voltage to the transistors.
An insulating layer of oxide is grown over the channel, then a conductive silicon or aluminum gate electrode is deposited, and a further thick layer of oxide is deposited over the gate electrode.
Each field-effect transistor consists of a channel in the semiconductor body of the device. Retrieved from ” https: International Trade Commission, ed. Since the whole memory array is exposed, all the memory is erased at the same time.
Cambridge University Press, p.
It was soon found that small-volume production was economical with EPROM parts, particularly when the advantage of rapid upgrades of firmware was considered. The same chip came in somewhat cheaper opaque OTP packages for production. Exposure time for sunlight of one week or three years for room fluorescent lighting may cause erasure.
The erasing window must be kept covered with an opaque label to prevent accidental erasure by the UV found in sunlight or camera flashes. Each bit of the word is a 1 or 0, depending on the storage transistor being switched on or off, conducting or non-conducting. In other words, to erase your EPROM, you would first have to X-ray it and then put it in an oven at about degrees Celsius to anneal semiconductor alterations caused by the X-rays.
While parts of the same size from different manufacturers are compatible in read mode, different manufacturers added different and sometimes multiple programming modes leading to 27521 differences in the programming process. Erasure, however, has to be accomplished by non-electrical methods, since the gate electrode is not accessible electrically.
Leaving the die of such a chip exposed to light can also change behavior in unexpected ways when moving from a windowed eeporm used for development to a non-windowed part for production. Development of the EPROM memory cell started with investigation of faulty integrated circuits where the gate connections of transistors had broken.
The effects of this process on the reliability of the part would have required extensive testing so they decided on the window instead. The process takes several minutes for UV lamps of convenient sizes; sunlight would erase a chip in weeks, and indoor fluorescent lighting over several years. A programmed EPROM retains its data for a minimum of ten to twenty years,  with many still retaining data after 35 or more years, and can be read an unlimited number of times without affecting the lifetime.
Presence of a voltage on this gate creates a conductive channel in the transistor, switching it on. This method of erasure allows complete testing and correction of a complex memory array before the package is finally sealed. A control gate electrode is deposited and further oxide covers it.
Photons of the UV light cause ionization within the silicon oxide, which allow the stored charge on the floating gate to dissipate. Because higher-density parts have little exposed oxide between the layers of interconnects and gate, ultraviolet erasing becomes less practical for very large memories.
As the quartz window is expensive to make, OTP one-time programmable chips were introduced; here, the die is mounted in an opaque package so it cannot be erased after programming — this also eliminates the need to test the erase function, further reducing cost.
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EPROM programming is slow compared to other forms of memory. Often this label was foil-backed to ensure its opacity to UV. The programming process is not electrically reversible. From Wikipedia, the eepdom encyclopedia.
ST Microelectronics – datasheet pdf
Once programmed, an EPROM can be erased by exposing it to strong ultraviolet light source such as from a mercury-vapor light. Non-volatile memory Integrated circuits Computer memory. When the 227512 voltage is removed, the electrons are trapped on the electrode. Stored charge on these isolated gates changed their properties. This page was last edited on 8 Novemberat The floating-gate electrode has no connections efprom other parts of the integrated circuit and is completely insulated by the surrounding layers of oxide.
However, as this was not universal, programmer software also would allow manual setting of the manufacturer and device type of the chip to ensure proper programming.
Paper data storage Drum memory Magnetic-core memory Plated wire memory Core rope memory s Thin-film 2751 Disk pack Twistor memory — Bubble memory — Floppy disk Magnetic tape Hard disk drive. Like EPROM chips, such microcontrollers came in windowed expensive versions that were used for debugging and program development.