Hardware manual

Rev. 3.0, 09/98, page 262 of 361
14.3.3 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 14.7 shows the recommended screening procedure.
Install
Note: * Baking time should be measured from the point when the baking oven reaches 150C.
Write and verify program
Read and check program
V
CC = 5.0V
Bake with power off
150C+10C, 48Hr
+ 8Hr*
– 0Hr
Figure 14.7 Recommended Screening Procedure
If a series of write errors occurs while the same PROM writer is in use, stop programming and
check the PROM writer and socket adapter for defects, using a microcomputer chip 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.