Everything You Need To Know About EPROM's


Pictured Above is a [CMOS] 128K Eprom, more on the CMOS is explained later on so don't worry about it for the time being.

Definition: an erasable programmable read-only semiconductor that can be user-programmed.

NM = The manucaturer's name abbreviated

27 = Tells that this device is only erasable by the use of a UV lamp. If this number was 28 then the device an be electronically erased and there would be no quartz window on the top of the device.

C  = Denotes CMOS technology which has low-power consumption & a wide range of voltage tolerances. This Particular chip suffers from lack of speed. CMOS gates are susceptible to static electrical discharge, so be careful when handling these devices.

128 = Designates this device as able of holding 128Kbits of data (16384 X 8 Bit)

150 = Access Time Of The Device, In This Case This Devices Access Time Is 150 nS (Nanonseconds)

Typical Access Times For 128K EPROM's is between 150 nS and 450 nS The higher the access time the more $$$ your going to pay for the device.

Inorder to program an EPROM you must apply a certain voltage to the 'programming pin' or the device. There are three types of voltages that can be used, but you must use the correct programming voltage for the device you are using or else you could damage the component. The 3 programming voltages are: +12.5 V (Most Common), +21 V (Least Common), & +25 V (Common). ( See the pin layout section for the pinout of the 128K EPROM showing the programming pin.

!! IMPORTANT!! An EPROM will suffer a dramatic drop in it's data retention reliability after 100 program/erase cycles. If there is continued use after this time then there is the possibility of data corruption. After 100 program/erase cycles it is recommended that the device be replace with a fresh new device.

Also note, Programmed data inside an Eprom can last up to 10 years. After 10 years of, normal usage, data corruption may occur. This is caused by the type of material used internally for the EPROM.

ATTENTION Autoroll Users Autoroll is most commonly burnt into a 128K EPROM. It does not matter what type of 128K EPROM there are 3 types: 27128, 27128A, 27C128. All of these will work, the only difference is price. There is no need for a high speed EPROM when using the autoroll software as there is no real benefit. It is possible to use the 28 Series of EPROM if you know how to erase this type. Also, it's possible to actually burn the autoroll software into a 256K EPROM and run successfully.

Simply take your run file and type the following at a dos prompt:

COPY /B AR602.RUN+AR602.RUN 602-256.RUN

the /B switch means to copy binary files the AR602.RUN+AR602.RUN means to combine these 2 files one after the other and to make one file 602-256.RUN

Do this will creat a 32K file which will nicely fit into a 256K EPROM

Then Simply burn this file and your done

* This helpful hint courtesy of: PNP, Thanx

ERASING AN EPROM

Erasing an EPROM is a very simple process. An EPROM must be exposed to a strong Ultraviolet light to be able to reset. The UV exposure is accomplished through the small quartz window on the top-side of the device. The standard time for complete erase of an EPROM is usually from 10 - 30 minutes. The erasure time is dependent on the wattage & intensity of the UV light being used. The higher the wattage of the bulb the more UV light emitted = faster erasure time! (The UV light causes current to flow across the pn-junction of the EPROM cause the device to be set to a logic 1, don't worry about this all you need to know is that it's erasing the device, just a technical note )

UV Erasers are available in 4 watt & 8 watt types, the 8 watt will erase in less time than the 4 watt

      

Pictured Above are the die's of a few EPROMs these are what is needed to be exposed to the UV light to cause it to be erased, thus the quartz crystal window.

!! WARNING !!

Do NOT leave an EPROM in a UV eraser for longer than 30 minutes! you will begin to damage & shorten the life of the device.

PROGRAMMING

Programming is fairly simple with every EPROM burner there must be software. Simply install the burner. There are 2 types (Internal Cards for PC's and some that work on the parallel) I have seen. Simply install the programmer and setup the software. Now comes the tricky part, kind of, in some of the newer software selection of the device isn't normally necessary because the programmer is able to recognize the type of device being programmed and apply the appropriate programming voltage to the correct pin, whereas older software and cheaper software which comes with the cheaper style of programmers, make you select the type of device from a list so you are using the correct algorithm to 'burn' the EPROM. Failing to select the proper component can cause damage to the EPROM or in some cases just not program the device with the correct data, requiring that you erase and start over. In some cases you will be able to program up to a certain point and then the software will stop or time out, this means you are not using the correct settings for the device you are programming, so erase the EPROM and start over and selecting the appropriate device from the list.

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The Information Provided On This Page Is For Education Use Only & To Aid In The Understanding Of How Various Scrambling Systems Are Used & How They Are Operated . . .

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