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I have an 'NE64 with two large external RAMs. The RAM needs to be
backed up when power goes off, but the NE64 does not. I have the
power sorted out, but I am wondering about the RAM chip selects. I
would like to guarantee that they are deselected by having a pullup on
the CE lines, but this means that the NE64 has power on two pins (I
selected Port H, more or less arbitrarily) while VDD is low.

Questions:
Will this forward bias the input protection network, and thus, the
entire NE64?

Is there an input protection network to worry about? The NE64 manual
doesn't say, or else I can't find it.

Are there better choices for external chip selects?

Gary Olmstead
Toucan Technology
Ventura CA


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