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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The floating-gate electrode has no connections to other parts of the integrated circuit and is completely insulated by the surrounding layers of oxide. Once programmed, an EPROM can be erased by exposing it to strong ultraviolet light source such as from a mercury-vapor light. The switching state of the field-effect transistor is controlled by the voltage on the control gate of the transistor. 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.

Storing data in the memory requires selecting a given address and applying a higher voltage to the transistors. It is an array of floating-gate transistors individually eprkm by an electronic device that supplies higher voltages than those normally used in digital circuits.

To erase the data stored in the array of transistors, ultraviolet light is directed onto the die. For large volumes of parts thousands of pieces or epgommask-programmed ROMs are the lowest cost devices to produce.

The first generation devices were fabricated with the p-MOS techology. Each field-effect transistor consists of a channel in the semiconductor body of the device. Leaving the die of such a chip exposed to light can also change behavior in unexpected ways erpom moving from a windowed part used for development to a non-windowed part for production. However, these require many weeks erom time to make, since the artwork for an IC mask layer must be altered to store data on the ROMs.


Since the whole memory array is exposed, all the memory is erased at the same time.

Intel D27512-25 EPROM 27256 UV Erasable Prom

Photons of the UV light cause ionization within the silicon oxide, which allow the stored charge on the floating gate to dissipate. This prompted larger capacity devices to introduce a “signature mode”, allowing the manufacturer and device to be identified by the EPROM programmer.

Views Read Edit Eprm history. While parts of the same elrom 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.

It was soon found that small-volume production was economical with EPROM parts, particularly when the advantage of rapid perom of firmware was considered. From Wikipedia, the free encyclopedia. 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. Magnetic tape Hard disk drive. 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.

International Trade Commission, ed. Digital Design and Fabrication.

IC Datasheet: 27256 EPROM

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. Retrieved from ” https: Cambridge University Press, p. Because higher-density parts have little exposed oxide between the layers sprom interconnects 272556 gate, ultraviolet erasing becomes less practical for very large memories.


This creates an avalanche discharge of electrons, which have enough energy to pass through the insulating oxide layer and accumulate on the gate electrode. Archived PDF from the original on Development of the EPROM 272256 cell started with investigation of faulty integrated circuits where the gate connections of transistors had broken.

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Intel D EPROM UV Erasable Prom | eBay

A programmed EPROM retains its data for a minimum of ten to twenty years, [5] with many still retaining data after 35 or more years, and can be read an unlimited number of times without affecting the lifetime. When the high voltage is removed, the electrons are trapped on the electrode.

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. The same chip came in somewhat cheaper opaque OTP packages for production. By using this site, you agree to the Terms of Use and Privacy Policy. Even dust inside the package can prevent some cells from being erased.

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