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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Initially, it was thought that the EPROM would be too expensive for mass production use and that it would be confined to development only. Often this label was foil-backed to ensure its opacity to UV.

It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages than those normally used in digital circuits. EPROM programming is slow compared to other forms of memory. In other projects Wikimedia Commons. 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. From Wikipedia, the free encyclopedia.

The switching state of the field-effect transistor is controlled by the voltage on the control gate of the transistor. It was soon found that small-volume production was economical with EPROM parts, particularly when the advantage of rapid upgrades of firmware was considered.

Like EPROM chips, such microcontrollers came in windowed expensive versions that were used for debugging and program development. This prompted larger capacity devices to introduce a “signature mode”, allowing the manufacturer and device to be identified by the EPROM programmer.

Intel D27512-25 EPROM 27256 UV Erasable Prom

To erase the data stored in erom array of transistors, ultraviolet light is directed onto the die. Computer memory that can retrieve stored data after a power supply has been turned off and back on is called non-volatile. Exposure time for sunlight of one week or three years for room fluorescent lighting may cause erasure.


In effect, the stored charge on the floating gate allows the threshold voltage of the transistor to be programmed. Development of the EPROM memory cell started with investigation of faulty integrated circuits where the gate connections of transistors had broken. For large volumes of parts thousands of pieces or moremask-programmed ROMs are the lowest cost devices to produce. When the high voltage is removed, the electrons are trapped on the electrode.

The programming process is not electrically reversible. The effects of this process on the reliability of the part would have required eprkm testing so they decided on the window instead. Because higher-density parts have little exposed oxide between the layers of interconnects and gate, ultraviolet erasing becomes less practical for very large memories.

Views Read Edit View history. Non-volatile memory Integrated circuits Computer memory. This method of erasure allows complete testing and correction of a complex memory array before the package is finally sealed. The floating-gate electrode has no connections to other parts of the integrated eprm and is completely insulated by the surrounding layers of oxide.

By using this site, you agree to the Terms of Use and Privacy Policy. 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. The recommended erasure procedure is exposure to UV light at Even dust inside the package can prevent some cells from being erased. Digital Design and Fabrication. 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.


A control gate electrode is deposited and further oxide covers it. Once programmed, an EPROM can be erased by exposing it to strong ultraviolet light source such as from a mercury-vapor light. 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.

Stored charge on these isolated gates changed their properties.

EPROM Technical Data

The erasing window must be kept covered with an opaque label to prevent accidental erasure by the UV found in sunlight or camera flashes. Photons of the UV light cause ionization within the silicon oxide, which allow the stored charge on the floating gate to dissipate.

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. Each bit of the word is a 1 or 0, depending on the storage transistor being switched on or off, conducting or non-conducting. International Trade Commission, ed. Magnetic tape Hard disk drive. Erasure, however, has to be accomplished by non-electrical methods, since the gate electrode is not accessible electrically.

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. Leaving the die of such a chip exposed to light can also change behavior in unexpected ways when moving from a eprim part used for development to a non-windowed part for production.