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CHAPTER 26
µ
PD78P054, 78P058
26.5 Erasure Procedure (
µ
PD78P054KK-T and 78P058KK-T Only)
With the
µ
PD78P054KK-T or 78P058KK-T, it is possible to erase ( or set all contents to FFH) the data contents
written in the program memory, and rewrite the memory.
The data can be erased by exposing the window to light with a wavelength of approximately 400 nm or shorter.
Typically, data is erased by 254-nm ultraviolet light rays. The minimum lighting level to completely erase the written
data is shown below.
• UV intensity × exposure time: 30 W
.s/cm
2
or more
• Exposure time: 40 minutes or more (using a 12 mW/cm
2
ultraviolet lamp. A longer exposure time may be
required in case of deterioration of the ultraviolet lamp or dirt on the package window).
When erasing written data, remove any filter on the window and place the device within 2.5 cm of the lamp tube.
26.6 Opaque Film Masking the Window (
µ
PD78P054KK-T and 78P058KK-T Only)
To prevent unintentional erasure of the EPROM contents by light and to prevent internal circuits from mulfunction
due to light coming in through the erasure window, mask the window with opaque film after writing the EPROM.
26.7 Screening of One-Time PROM Versions
One-time PROM versions (
µ
PD78P054GC-3B9, 78P054GC-8BT, 78P054GK-BE9, 78P058GC-8BT, and
78P058YGC-8BT) cannot be fully tested by NEC before shipment due to the structure of one-time PROM. Therefore,
after users have written data into the PROM, screening should be implemented by user: that is, store devices at
high temperature for one day as specified below, and verify their contents after the devices have returned to room
temperature.
Storage Temperature Storage Time
125°C 24 hours
For users who do not wish to implement screening by themselves, NEC provides such users with a charged
service in which NEC performs a series of processes from writing one-time PROMs and screening them to verifying
their contents for users by request. The PROM version devices which provide this service are called QTOP
TM
microcontrollers. For details, please consult an NEC sales representative.