Re[2]: asserted, de-asserted

["Arlen P. Walker" <Arlen -dot- P -dot- Walker -at- JCI -dot- COM>]

      If you do not use the word deasserted, and the engineer catches it, he
      will simply mark it to be changed back to deasserted. I belive that there
      is a technical reason for the use of teh word deasserted.

The "technical reason" has to do with clarity. Time was when you simply wrote
such-and-such a line (or signal) was "raised" or "held high." This referred to
the voltage on the line ("high" voltage was a "1" or "true" in digital terms).
But design constraints caused some signal lines to assert the condition with a
low (0 or "false") signal. Traditionally this was signified by drawing a
horizontal line over the signal name (the traditional logical symbol for "not").
"Read" with a line above it was pronounced "not Read."

This is hard to get across in ASCII documentation (used frequently for working
notes) and it's quite possible to misunderstand it even in typeset documents.
(Imagine the condition above: When the microprocessor raised the "not Read" line
it signalled a write operation. Now think of reading a statement to that effect
in an engineer's ASCII design notes file, without the benefit of the horizontal
line -- "When the microprocessor raises the Read line it signals a write
operation.")


Have fun,
Arlen


Arlen -dot- P -dot- Walker -at- JCI -dot- Com
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