在不同电压下擦除和编程失败

与18LF1320一起工作，用ICD-3编程，我一直在尝试从ICD-3提供的各种VDD电压。我注意到一些偶然的验证失败。我怀疑问题是用VDD＝+4.5V编程，然后试图在VDD＝+2.875 V下擦除。我在VDD＝+4.5V编程，然后在VDD＝+2.85 V上进行了明确的闪存擦除，然后读取和查看程序存储器。绝对没有被抹去。每一点都和编程之后一样。然后我将VDD提升到+3.25，并重复擦除。这一次，事实上，一切都被抹去了。看起来，如果每个程序在一个更高的VDD上，你可能无法重新编程它在一个较低的VDD，除非你首先擦除它在同一个更高的VDD。



      以下为原文

    Working with a 18LF1320, programming with an ICD-3, I have been trying various Vdd voltages supplied from the ICD-3.  I noticed some occasional verify failures.  I suspected the problem is programming with Vdd=+4.5v and then trying to erase at Vdd=+2.875v.  I verified this is true.  I programmed at Vdd=+4.5v, then did an explicit Flash erase at Vdd=+2.85v, then a Read and View Program Memory.  Absolutely nothing was erased.  Every bit was exactly as it was after the programming.  Then I raised Vdd to +3.25 and repeated the erase.  This time everything was in fact erased.  It looks like if you every program a device at a higher Vdd, you may not be able to re-program it at a lower Vdd unless you first erase it at that same higher Vdd.