HD6475348R Datasheet, PDF (330/487 Pages) Hitachi Semiconductor – Single-Chip Microcomputer

17.5 Reliability of Written Data
An effective way to assure the data holding characteristics of the programmed chips is to bake
them at 150˚C, then screen them for data errors. This procedure quickly eliminates chips with
PROM memory cells prone to early failure.
Figure 17-8 shows the recommended screening procedure.
Write program
Bake with power off
150^°C 48 Hr
Read and check program
VCC = 5.0 V
Install
Figure 17-8 Recommended Screening Procedure
If a series of write errors occur while the same PROM writer is in use, stop programming and
check the PROM writer and socket adapter for defects, using a microcomputer with a windowed
package and on-chip EPROM.
Please inform Hitachi of any abnormal conditions noted during programming or in screening of
program data after high-temperature baking.
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