Filter
Top Products
MaxLoader User’s Guide
68
NOTE: Erasing EPROMs. In order to clear data in an EPROM, the chip
should be exposed to a short wave UV (Ultra violet) light. Most erasers require
between 5 and 30 minutes erasing an EPROM. Some types of chips take longer
to erase than others. An EPROM based part (a PLD or Microcontroller) with a
security bit feature is designed so that the security address is typically the last
bit to be erased. If the window of a chip is not clear, try cleaning the window
with alcohol or a solvent. Erase chips if the chips are exposed to sunlight and
fluorescent light for months or years; your chips can be erased. You should
cover the window of the programmed chips with an opaque label to make the
data permanent. Some EPROM based parts can't be erased because they do
not have a window. These chips are called one time programmable (OTP)
EPROMs.
An EPROM has a quartz window located on the chip just above the die. An
EPROM is erased by exposing it to high-frequency ultra-violet light waves.
Erasing an EPROM usually takes from 15-20 minutes, but may be shorter or
longer, depending on the device. Many manufacturers make EPROM erasers. If
you wish to purchase an eraser, call EE TOOLS at 408-263-2221,
sales@eetools.com. When an EPROM is not being erased, the window may be
covered with an opaque label. Sometimes (over a period of years) an EPROM
will start to erase due to the level fluorescent light in the room. Direct exposure
to sunlight also has this effect and happens much more rapidly and commonly.
NOTE: In order to decide if the device is blank, the user should read the target
device. If the buffer is filled with all FFs or 00s, the device is most likely in an
erased or unprogrammed state; otherwise, the device is not erased.
CAUTION: Some devices such as Philips P98C52 can pass the BLANK
CHECK routine after they are secured even though they are not blank.