Fujitsu F2MC-8L MB89620 Series Hardware Manual page 315

D Programming Specifications for One-time PROM and EPROM Microcontrollers
D.1 Programming Yield and Erasure
This section describes the programming yield and the data erasure on EPROM
microcomputer.
n Programming Yield
All bits cannot be programmed at Fujitsu shipping test to a blanked OTPROM microcomputer,
due to its nature. For this reason, a programming yield of 100% cannot be assured at all times.
n Notes on Using and Data Erasure on EPROM Microcomputer
l Erasure
In order to clear all locations of their programmed contents, it is necessary to expose the
internal EPROM to an ultraviolet light source. A dosage of 10 W-seconds/cm
completely erase an internal EPROM. This dosage can be obtained by exposure to an
ultraviolet lamp (wavelength of 2537 Angstroms (Å)) with intensity of 12000 µ W/cm
minutes. The internal EPROM should be about one inch from the source and all filters should be
removed from the UV light source prior to erasure.
It is important to note that the internal EPROM and similar devices, will erase with light sources
having wavelengths shorter than 4000 Å. Although erasure time will be much longer than with
UV source at 2537 Å, nevertheless the exposure to fluorescent light and sunlight will eventually
erase the internal EPROM, and exposure to them should be prevented to realize maximum
system reliability. If used in such an environment, the package windows should be covered by
an opaque label or substance.
294
APPENDIX
2
is required to
2
for 15 to 21
MB89620 series