EPROM erase process
Four different EPROM with 64kByte (512 kBit) were used for the
test. Reading was done with a custom reading device. A special software read out
the EPROM content every 2 seconds and generated a 256 x 256 pixel gray scale image.
Every pixel represents a byte, 0 is shown as black and 255 as white.
Before the erasing all bytes of the EPROM were programmed to 0.
The erasing was done with a simple UV EPROM-Eraser.
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AM27C512-150DC
AMD CMOS EPROM von 1994
Datasheet extract: "AMD's CMOS process technology provides high speed, low power, and high noise immunity." ca. 3-4 minutes erasing time |
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D27512-2
intel NMOS EPROM
ca. 2 minutes erasing time |
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TMM27512AD-17
TOSHIBA NMOS EPROM von 1988
Datasheet extract: "The TMM27512AD is fabricated with the N-channel silicon double lyer gate MOS technology." < 2 minutes erasing time |
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TMS27C512-15JL
Texas Instruments CMOS EPROM von 1991
ca. 2 minutes erasing time |
After 3 minutes all tested EPROMs seemed to be erased when read with 5V.
When the voltage is lowered down to 3V, data recovers.
A complete erasing was given after 10 minutes.
Interesting are also the shadings (TI & intel).
Also can be seen that single bits need much longer than the remaining memory.
