HD6433308 Datasheet, PDF (259/349 Pages) Hitachi Semiconductor – Hitachi Single-Chip MicroComputer

13.3.2 Notes on Writing
(1) Write with the specified voltages and timing. The programming voltage (Vpp) 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 Intel specifications or Hitachi HN27256 or HN27C256 specifications,
VPP 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.
13.3.3 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 13-6 shows the recommended screening procedure.
Write program
Bake with power off
150° ± 10°C, 48 Hr ^{+ 8 Hr *}
– 0 Hr
Read and check program
Vcc = 4.5V and 5.5V
Install
Note: Baking time should be measured from the point when the baking oven reaches 150°C.
Figure 13-6. Recommended Screening Procedure
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