On Sun, May 27, 2018 at 3:10 PM, Noel Chiappa via cctalk <
cctalk at classiccmp.org> wrote:
I decided I'd do an article about the Term-Mite
for the CHWiki; I found
Ciarcia's long article about the Term-Mite (in his book, which Google books
has); it talks throughout the article about the NS455 - but it also says
"[t]he Term-Mite actually uses a NS405 chip which is a specialized version
the generic NS455".
The NS455 has firmware in masked ROM, which it uses if the EA pin is low.
If EA is high (min spec 3.8V, normally tied directly to Vdd), external
memory (usually ROM or EPROM) must be used instead.
The NS405 has the masked ROM disabled, so external firmware must be used,
and EA must be tied high. It is actually the same die with unspecified ROM
content, so it probably would execute some sort of internal firmware if EA
was low, but that might or might not be the same as the standard NS455
firmware; it could be firmware from a custom version of the NS455, or test
firmware, or (less likely) any of the above but with some errors due to
I've been searching for the NS405 manual (not the datasheet) for a very