Thanks to comments I've received, particularly from Curtis Clark, some further
adjustments to the BIRD 187 text are needed.
In addition to incorrect usage of the word "Type", a particular sentence
causing concern in the current BIRD is, "Unless otherwise noted, Usage Out
arguments or data of Value or Default provided as Format are effectively
ignored by EDA tools."
This is actually incorrect. In addition, nearly-identical rules are repeated
on page 202 under "Combination and Corner Rules", as well as under the
"Default" Reserved Word definition.
To simplify and correct the BIRD and the IBIS document generally, four simple
rules should be stated early in the specification, and preferably only once or
twice:
- Usage Out parameters, except Table, are ignored by EDA tools, except
for display formatting purposes
(e.g., EDA tools may wish to distinguish between Usage Out String
vs. Usage Out Float for presentation to the end user)
- Default is prohibited with Usage Out
- Default is prohibited with Formats DjRj, Dual-Dirac, Gaussian, and
Table
- Default and Format Value are mutually exclusive and cannot be used
together for the same parameter
If we removed the first sentence under Combination and Corner Rules on page
202, and also removed the "ignored by EDA tools" line under Format noted above,
and replaced both with sentence versions of the bullets above, would that be
adequate to define the interaction rules for Default, Usage Out, and Format?
- MM
