RAIL Revision Or Apendage Document  (ROAD)

ROAD ID#:      3.1
ISSUE TITLE:   Order of RAIL Keywords
REQUESTOR:     Bob Ross, Interconnectix, Inc.
DATE SUBMITTED:                       April 24, 1996
DATE ACCEPTED BY RAIL WORKGROUP:      May 2, 1996

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STATEMENT OF THE ISSUE:

Certain keywords contain definitions needed by others.  In order to allow
a one-pass reading of a RAIL file, the order of certain keywords needs
to be specified.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

Add an Other Notes secton in [RAIL Title]:

| Other Notes:  Several keywords that are described below must be positioned
|               in the following order so that definitions are presented
|               before usage:
|                    [Unit Length]     Required
|                    [Stackup]         Optional
|                    [Map Table]       Required
|                    [Multiboard]      Optional
|                    [Group Nets]      Optional
|                    [Group Parts]     Optional
|                    [DC Nets]         Optional
|                    [Trace Char]      Required
|               The remaining keywords except [End] may be in any order 
|               following [Trace Char].  The final keyword in the file
|               must be [End]. 

Also put the definitions of contrained keywords in the above order.

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

[Unit Length] and [Stackup] are traditionally specified first.

[Map Table] contains generic_name and ref_des definitions.

[Multiboard] may not fully defined in RAIL, but the place is reserved because
it defines connector ref_des defintions that may be used later.

[Group Nets], [Group Parts] and [DC Nets] have definitions needed by other
keywords, particularly [Topology]

[Group Parts] may use generic_names.

[DC Nets] defines net_names that may be used by [Topology]

[Trace Char] needs [Unit Length] and may use net_names and group_names defined
under [Group Nets].  Also, the defined [Stackup] may provide some Z0/Td values
which might optionally be checked against the range of [Trace Char] values
given as a default and for various net_names and group_names.

All of the definitions are in place before other keywords are encountered.
The keywords that are not constrained are [Topology], [Priority], [Budgets],
[Clocks], [Clock Skew], and [Edge Sens].

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ANY OTHER BACKGROUND INFORMATION:

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