11.3.2 Notes on Writing
(1) Write with the specified voltages and timing. The programming voltage (V
PP
) is 12.5V.
Caution: Applied voltages in excess of the specified values can permanently destroy the chip. Be
particularly careful about the PROM writer’s overshoot characteristics.
If the PROM writer is set to Hitachi HN27256 or HN27C256 specifications, or to Intel
specifications, V
PP
will be 12.5V.
(2) Before writing data, check that the socket adapter and chip are correctly mounted in the
PROM writer. Overcurrent damage to the chip can result if the index marks on the PROM writer,
socket adapter, and chip are not correctly aligned.
(3) Don’t touch the socket adapter or chip while writing. Touching either of these can cause
contact faults and write errors.
11.3.3 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 11-7 shows the recommended screening procedure.
236
Summary of Contents for H8/326 Series
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