Capture to Allegro Interface
Tim Brandis and Moji Friedholf
Cadence Design Systems, Inc.
What is the Capture to Allegro interface?
 Before the 9.2.1 release, Capture used the third party interface
to create a netlist, a unused pin list, and many device files.
 With the 9.2.1 release, Capture uses a modified version of the
Concept netlister (called PXLLite) to produce three ASCII files.
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– The new interface does not use device properties, instead all the
part properties are placed into the PSTCHIP.DAT file.
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– All of the net properties are included in the PSTXNET.DAT file.
– The PSTXPRT.DAT file (the expanded part list) lists each
reference designator and the sections assigned to it.
CONFIGURATION FILE
 The configuration file specifies net, part (function), component instance and
component definition properties. This mapping determines which properties may
be netlisted from Capture to Allegro or back annotated from Allegro to Capture. If
a Capture property is not included in the configuration file it is not passed to
Allegro. Similarly, if an Allegro property is not listed in the file, it does not get
back annotated to Capture.
 The configuration file is divided into four sections, written in a Windows .INI
format.
 ComponentDefinitionProps Allegro component definition properties, output in
PSTCHIP.DAT file
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 ComponentInstanceProps Allegro component instance properties, output in
PSTSPRT.DAT file
 netprops Allegro net properties, output in the PSTXNET.DAT file
 functionprops Allegro function properties, output in the PSTXPRT.DAT file
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 You can have many different configuration files. All you need do is specify which
file you want to use in the Setup dialog box.
 A list of typical properties used with Allegro may be found in the Capture-Allegro
filter of the property editor. This filter is built on the PREFPROP.TXT file, which is
copied to your Capture directory during installation.
Why did we make the change? What do we
get with the new interface?
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 The third party interface gets the job done but the connection
between the schematic and board file is tenuous at best. Back
annotation was unstable and would often crash.
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 The third part interface was quite lax in checking for correct
properties and could create a netlist that would require a lot of
work to bring into Allegro.
 The PXLLite interface allows Capture access to a robust back
annotation process, design reuse modules (for 14.1), and
constraint management (for 15.0).
What are the costs of the new interface?
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 Tighter integration with Allegro requires that a lot more work
occurs on the front end. In the old interface this work would be
done at the Allegro end.
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 Use of Concept style netlister requires the user to deal with
legacy Concept/Allegro integration issues.
 The interface is still, in many ways, in its infancy. Issues are
appearing as more an more customers create netlists from real
world designs
 Our customers (and the support engineers) have to learn a new
interface that has completely different requirements.
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What are customers going to see that are
familiar with the old interface.
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 Boards that use to work in 9.2 will likely be unable to run
through the new interface without a number of errors.
 Engineers on the schematic side are going to be spending more
time creating netlists since the interface is nitpicky.
 Engineers on the board side are going to be spending less time
fixing problems with the netlists.
 If a customer has made significant investments in creating
libraries to work with the third party interface are going to have
to rework their libraries.
What are the major problems?
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 DEVICE properties dealt with differently between the two
interfaces. (Errors: Alg0011, Alg0013, Alg0014, Alg0016)
 Parts with multiple power pins that have the same name are
going to cause errors. (Errors: Alg0045, Alg0050)
 Parts without pin numbers will cause errors. (Error: Alg0031)
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DEVICE properties
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 Problem:
– The third party interface all parts had to have a DEVICE property that
would specify which device file the part information would end up in. In
most cases all parts that shared the same PCB footprint would share the
same DEVICE property.
– The PXLLite interface considers that all parts with the same DEVICE
property are the same part.
 Consequence:
– If a customer has setup a design for the third party interface and they
netlist it in the PXLLite interface all parts that share the same device
property but are not exactly the same will flag and error.
 Solution:
– Remove the device properties from the design
Power pins with the same name
 Problem:
– Concept requires that all power pins on a part have unique pin
names.
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 Consequence:
– This was not a requirement in the old interface and has never
been a requirement within Capture. Many parts in the Capture
supplied libraries are actually build with multiple power pins that
are the same name.
 Solution
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– An ISR has been released that fixes this error.
Parts with no pin numbers
 Problem:
– The PXLlite interface requires that all parts have pin name and
pin numbers.
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 Consequence:
– This was not a requirement of the old interface and customers
may have spent a lot of time creating libraries that will not work
with the new interface. This is primarily a problem with two or
three terminal devices.
 Solution:
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– Go into the library and add pin numbers to all pins on all parts.
Other issues that may come up
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 Parts with conflicting value of Power Pin visible.
 Lower case reference designator names crash Allegro netin.
 Primitive names with trailing spaces
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 Parts with no pins cause netlist error.
 Power pin visibility. (Error: Alg0048)
 Invalid Characters. (Error: Alg0037, Alg0038, ALG0051,
Alg0052)
 All pins on the part are power pins. (Error: Alg0053)
 No Connect pins: (Error: Alg0049)
Invalid Characters
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 As per latest doc of ConceptHDL Library Reference Manual, the following are
invalid character for pin names as well as net names in Flow: PCRNUM 403634
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 1.
 2.
All Extended character set
/
 3.
;







4.
5.
6.
7.
8.
9.
10.
!
<
>
:
\
"
,
 Currently if we see Capture-Allegro flow few of these chars are valid too Ex: <, >.
 Once if we start supporting Vector pins, < and > will become invalid chars in pin
names.
When in doubt use the help
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 The online help for this release is quite good. Reasonably clear
descriptions and a number of good examples. Pretty much
anything you might have a question about is covered in the
manual.
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