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CHAPTER 23
μ
PD78P018F, 78P018FY
23.4 Erasure:
μ
PD78P018FDW, 78P018FKK-S
μ
PD78P018FYDW, 78P018FYKK-S
The data written to the program memory of the
μ
PD78P018FDW, 78P018FKK-S, 78P018FYDW and
78P018FYKK-S can be erased (to FFH) and new data can be rewritten to it.
To erase the data contents, cast a light whose wavelength is shorter than approximately 400 nm onto the erasure
window. Usually, an ultraviolet ray of 254 nm is used. The light intensity and time required to completely erase the
data contents are as follows:
Intensity of ultraviolet ray
×
erasure time: 30 Ws/cm
2
min.
Erasure time: 40 minutes or longer (with an ultraviolet lamp of 12 mW/cm
2
. However, the erase time may be
extended if the performance of the ultraviolet lamp is degraded or if the erasure window is dirty.)
To erase the data, place the ultraviolet lamp at a distance of within 2.5 cm from the erasure window. If a filter
is attached to the ultraviolet lamp, remove the filter before casting ultraviolet ray.
23.5 Erasure Window Sticker:
μ
PD78P018FDW, 78P018FKK-S
μ
PD78P018FYDW, 78P018FYKK-S
To protect from accidental erasure by light sources other than that of the EPROM eraser, and to protect internal
circuit other than the EPROM from misoperation due to light, stick a protective sticker over the erasure window when
EPROM erasure is not being performed.
23.6 Screening of One-Time PROM Model
Because of their structure, the one-time PROM models (
μ
PD78P018FCW, 78P018FGC-AB8, 78P018FGK-8A8,
78P018FYCW, 78P018FYGC-AB8, and 78P018FYGK-8A8) cannot be completely tested by NEC before shipment.
It is recommended that screening be implemented to verify the PROM contents after necessary data have been written
to the PROM and the product has been stored under the following temperature conditions:
Storage Temperature
Storage Time
125
°
C
24 hours
NEC offers a service, at a charge, called QTOP
TM
microcontroller, for writing, marking, screening, and verifying
one-time PROMs. For details, consult NEC.