All,
I sent this e-mail to IBIS-Interconnect in May. They have been very busy, so
we might want to discuss this in today's IBIS-ATM meeting.
The following documents four levels of ISS parsing. I did all from this from
memory, so details may be wrong or missing.
Level 1 Parser
Evaluate the legality of each subckt line independently of the rest of the
subckt.
Read one "SPICE Line". A "SPICE Line" is an ASCII string that combines lines
that have a + continuation character in the first character of following
lines.
Note that comment lines (* in column 1) may be the middle of + continuation
lines (I am not sure if this is true).
Tokenize the line.
What are token separators?
White space
Commas
Tabs
CR/LF
= "x=3.7" "x = 3.7"
' Strings
Note that SPICE is case insensitive, except inside of strings
First token of any line must be:
If first character is "."
.subckt
.ends
.include
.model
If first character is "*"
Comment line and must be ignored
Or one of the following legal "Instance Name" characters ("Instance Type")
X
R
C
L
G
.
Instance Name Rules
Character set [a-z], [A-Z], "_", ..
Each "Instance Type" specifies which tokens are
Nodes
And which Nodes are Reference Nodes
Rules on Node Names
Character set
First character rules
Name
Model Name
Subckt Name
Reserved Name
Case sensitive string name (usually files or environmental variables)
Integer Numbers
Parameters
Computation
Floating Point Numbers
Engineer Notation Rules (different than IBIS)
E, D notations
Parameters
Computation
Each "Instance Type" specifies which parameters (Name=Value) are
Names Rules
Required Reserved Names
Optional Reserved Names
Optional Non-Reserved Names
Value Rules for
Reserved Names
Non-Reserved Names
Level 2 parser
Understands the following structure
.subckt x
.subckt y
.ends y
.ends x
Within a .subckt/.ends range:
Generates a list of Node Names and number of times each node is referenced
Reports if any Node Name (other then reference nodes) appear only once
Level 3 parser
Flatten all .include statements
Identify if any string is a file name, and if so, make sure that file exists
Identify if any string is a subckt name, and if so, make sure that subckt is
defined
Identify if any string is a model name, and if so make sure that model
exists
Level 4 parser
Verify subckt and model scoping rules
Personally, I think we can rely on HSPICE and any of our SPICE simulators to
verify level 2, 3, 4 rules. I therefor propose that we implement the level 1
parser.
Walter
