Donor challenge: Your generous donation will be matched 2-to-1 right now. Your $5 becomes $15! Dear Internet Archive Supporter,. I ask only. The Intel is a 5V only, ,bit Ultraviolet Erasable (Cerdip)/plastic production reside in a EPROM directly on a system’s memory bus. D K (32Kx8) uv EPROM in a 28 pin CERDIP package by Intel. Download Intel D datasheet: Status: NOS (New Old Stock), perfect condition.

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Like EPROM chips, such microcontrollers came in windowed expensive versions that were used for debugging and program development. To erase the data stored in the array of transistors, ultraviolet light is directed onto the die. From Wikipedia, the free encyclopedia. This method of erasure allows complete testing and correction of a complex memory array before the package is finally sealed. The recommended erasure procedure is exposure to UV light at Storing data in the memory requires selecting a given address and applying a higher voltage to the transistors.

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 perom gate to its initial, uncharged condition photoelectric effect. In other projects Wikimedia Commons.

EPROM Technical Data

Each field-effect transistor consists of a channel in the semiconductor body of the device. Non-volatile memory Integrated circuits Computer memory. 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 eprkm 8-bit byte of storage to the output buffer amplifiers.

Magnetic tape Hard disk drive. The programming process is not electrically reversible.

The first generation devices were fabricated with the elrom techology. 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 e;rom be erased after programming — this also eliminates the need to test the erase function, further reducing cost.


Each bit of the word is a 1 or 0, depending on the storage transistor being switched on or off, conducting or non-conducting.

Cambridge University Press, p. By using this site, you agree to the Terms of Use and Privacy Policy. Photons of the UV light cause ionization within the silicon oxide, which allow the stored charge on the floating gate to dissipate.

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. It was soon found that small-volume production was economical with EPROM parts, particularly when the advantage of rapid upgrades of firmware was considered.

27256 – 27256 256K EPROM Datasheet

This page was last edited on 8 Novemberat Often this label was foil-backed to ensure its opacity to UV. Erasure, however, has to be accomplished by non-electrical methods, since the gate electrode is not accessible electrically. However, these require many weeks lead time to make, since the artwork for an IC mask layer must be altered to store data on the ROMs. Once programmed, an EPROM can be erased by exposing it to strong ultraviolet light source such as from a mercury-vapor light.

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 subtle differences in the programming process. For large volumes of parts thousands of pieces or moremask-programmed ROMs are the lowest cost devices to produce. Source and drain contacts are made to regions at the end of the channel.

Stored charge on these isolated eprkm changed their properties. When the high voltage is removed, the electrons are trapped on the electrode. A control gate electrode is deposited and further oxide covers it.

The same chip came in somewhat cheaper opaque OTP packages for production. Development of the EPROM memory cell started with investigation of faulty integrated circuits where the gate connections of transistors had broken. This prompted larger capacity devices to introduce a “signature mode”, allowing the manufacturer and device to be identified by the EPROM programmer. 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.


Retrieved from ” https: International Trade Commission, ed. EPROM programming is slow compared to other eprm of memory. Views Read Edit View history. The switching state of the field-effect transistor is controlled by the voltage on the control gate of the transistor. EPROMs are easily recognizable by the transparent fused quartz window in the top of the package, through which the silicon chip is visible, and which permits exposure to ultraviolet light during erasing.

5x 27C Kb 32Ko UV eprom

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. This creates an avalanche discharge of electrons, which have enough energy to pass through the insulating oxide layer and accumulate on the gate electrode.

The floating-gate electrode has no connections to other parts of the integrated circuit and is completely insulated by the surrounding layers of oxide. Since the whole memory array is exposed, all the memory is erased at the same time. 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.

27256 EPROM

A programmed EPROM retains its data for a minimum of ten to twenty years, [5] with many still 27265 data after 35 or more years, and can be read an unlimited number of times without affecting the lifetime. Digital Design and Fabrication. Because higher-density parts have little exposed oxide between the layers of interconnects and gate, ultraviolet erasing becomes less practical for very large memories.