6 screening of one-time prom versions – NEC uPD78P078 User Manual
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CHAPTER 27
µ
PD78P078, 78P078Y
27.4 Erasure Procedure (
µ
PD78P078KL-T and 78P078YKL-T Only)
With the
µ
PD78P078KL-T or 78P078YKL-T, it is possible to erase (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 x erasure time: 30 W·s/cm
2
or more
• Erasure time: 40 minutes (using a 12 mW/cm
2
ultraviolet lamp. A longer erasure 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.
27.5 Opaque Film Masking Window (
µ
PD78P078KL-T and 78P078YKL-T Only)
To prevent unintentional erasure of the EPROM contents by light and to prevent internal circuits from malfunction
due to light coming in through the erasure window, mask the window with the attached opaque film after writing
the EPROM.
27.6 Screening of One-Time PROM Versions
One-time PROM versions cannot be fully tested by NEC before shipment due to the structure of one-time PROM.
Therefore, after users have written data to the PROM, screening should be implemented: that is, store devices under
the following conditions. Then verify their contents after the device 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. This service will soon be available for the
µ
PD78P078Y. For details, please consult an NEC sales
representative.