NEC 78014Y Series, User Manual

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CHAPTER 22
µ
PD78P014, 78P014Y
501
22.3 Erasure Characteristics (for
µ
PD78P014DW, 78P014YDW)
Through exposure to light having a very short wavelength of less than 400 nm, contents of the programmed data
can be erased (FFH).
The
µ
PD78P014DW and 78P014YDW program memory contents are usually erased by ultraviolet rays having
a wavelength of 254 nm. The amount of exposure needed to completely erase the
µ
PD78P014DW and 78P014YDW
is at least 15 W
×
s/cm
2
(ultraviolet ray strength
×
erasure time). The erasure time is about 15 to 20 minutes (when
using a 12000
µ
W/cm
2
ultraviolet ray lamp). However, the required erasure time may be longer in some cases, such
as when there has been deterioration of ultraviolet ray lamp performance or when the erasure window is dirty. When
erasing, place the
µ
PD78P014DW and 78P014YDW within 2.5 cm of the ultraviolet ray lamp. If a filter has been
attached to the ultraviolet ray lamp, remove the filter before erasing.
22.4 Opaque Film on Erasure Window (for
µ
PD78P014DW, 78P014YDW)
When erasing EPROM contents, be sure to cover the erasure window with a shading film to prevent unintentional
erasure of EPROM contents by light source other than the ultraviolet ray lamp and to prevent a light source from
unintentionally affecting internal circuits other than the EPROM.
22.5 Screening of One-Time PROM Versions
Because of their construction, one-time PROM versions (
µ
PD78P014CW, 78P014YCW, 78P014GC-AB8, 78P014YGC-
AB8) cannot be fully tested by NEC before shipment. After the necessary data has been written, it is recommended
that screening is implemented in which PROM verification is performed after high-temperature storage under the
following conditions.
Storage Temperature Storage Time
125
°
C 24 hours
NEC is offering one-time PROM writing to marking, screening and verifying with charge under the name QTOP
TM
microcontroller. Please contact an NEC sales representative for the details.