HD6433640 HITACHI [Hitachi Semiconductor], HD6433640 Datasheet - Page 122

• Manufacturer Part Number: HD6433640
• Description: H8/3644 Series Hardware Manual
• Manufacturer: HITACHI [Hitachi Semiconductor]

6.3.3
A highly effective way to improve data retention characteristics is to bake the programmed chips
at 150 C, then screen them for data errors. This procedure quickly eliminates chips with PROM
memory cells prone to early failure.
Figure 6.6 shows the recommended screening procedure.
If a series of programming errors occurs while the same PROM programmer is in use, stop
programming and check the PROM programmer and socket adapter for defects, using a
microcomputer with on-chip EPROM in a windowed package, etc. Please inform Hitachi of any
abnormal conditions noted during or after programming or in screening of program data after
high-temperature baking.
6.4
6.4.1
Table 6.6 illustrates the principle of operation of the on-chip flash memory in the H8/3644F,
H8/3643F, and H8/3642AF.
Like EPROM, flash memory is programmed by applying a high gate-to-drain voltage that draws
hot electrons generated in the vicinity of the drain into a floating gate. The threshold voltage of a
programmed memory cell is therefore higher than that of an erased cell. Cells are erased by
grounding the gate and applying a high voltage to the source, causing the electrons stored in the
Reliability of Programmed Data
Flash Memory Overview
Principle of Flash Memory Operation
Figure 6.6 Recommended Screening Procedure
Bake chip for 24 to 48 hours
Read and check program
verify programmed data
Program chip and
at 125 C to 150 C
with power off
Install
113