ipc356
IPC-D-356 & NTD NETLIST FORMA T
The following are some of the basic guidelines used to enhance the IPC-D-356 netlist test specification. These are a suggestion which are in use today by several CAD/CAM software companies. Support of the IPC-D-356 standard with NTD format, provide the user with the ability for netlist compare , netlist test and fixturing and computer aided repair.
GENERAL GUIDELINES
1. For the Pad definition for a round feature , the pad size should be placed in the X field of the pad dimension. The Y field should be set to zero. Doing so allows the distinction between round and square features. (Square has both values set).
2. Non Plated Drill holes should be output as 367 records. These are typically used to tool the PCB to the test fixture.
3. The Midpoint flag should be included and Midpoint records should be output when test point elimination or Net End routines are performed. This information can be useful in reducing test points in fixturing while still being available during computer aided repair.
4. When Midpoint elimination is done and PTH endpoints can be identified as to a preferred side to test (testing for hole voids), the access side should be set to the layer number rather than A00.
5. When Soldermask is used, the soldermask information should be output. This is critical when building test fixtures and performing netlist test.
6. When possible , Trace/Track information should be output in the NTD specification. This will be used by computer aided repair systems (NTD = Net Trace Data)
7. When outputting pads for Rounded Rectangles , Ovals or Chamfered Rectangles , the pad dimension should be output as a rectangle. This information will allow for proper pin placement and staggering in test. The netlist has been created at this point and net compare or DRC should not be affected by this presentation.
8. When blind vias are used in the design , PTH records should be output as a 317 record with the access side set to the layer that the PTH can be tested from.
IPC-D-356 ELECTRICAL TEST SPECIFICATION
NETLIST RECORDS
Every record consists of a line of 80 characters , referred to as columns.
Operation Code Definition (columns 1-3)
Column 1    3 = Start of test point record
C = Comment Information
Column 2    1 = Feature & Through hole
2 = Feature Only (SMD , )
5 = Tooling Feature (defined as such in the original data source)
6 = Tooling hole (defined as Non Plated Holes)
Column 3 7 = This file is using the standard electrical TEST record format
Signal Identification Field (columns 4-20)
Columns 4-17 = Net Name / Node Number
N/C (in columns 4-6) = single point net / Isolated point
Component Identifier Field (columns 21-32)
Columns 21-26 = Reference Designator (Device nomenclature)
Column 27 = “-” A Dash to separate the reference designator from pin identifier Columns 28-31 = The pin identifier. (Pin Number)
Column 32 May contain M to indicate a Mid Net point. Other wise left blank.
Hole Definition Field (columns 33-38)
Column 33  = “D” Drilled Hole Identifier . Left blank if not drilled
Columns 34-37 = The Hole diameter in 0.0001 Inch or 0.001 mm.
Column 38 = “P” Indicates Plated Through hole
= “U” Indicates Unplated Through hole
Test Point Access Field  (columns 39-41)
Column 39 = “A”  Access Code
Columns 40-41 = “00”  Test point is accessible from both sides (PTH)
= “01”  Test point is accessible from side 1 (Primary side)
= “0n”  Test pont is accesible from side “n” where “n” is usually the last outer
layer
Test Point Location Field (columns 42-57)
Column 42 = Shall contain “X” to specify X location
Column 43 = “+” or “-” or blank to specify the sign (blank = “+”)
Columns 44-49  = Shall contain six digits representing the X coordinate in 0.0001 Inch or
0.001mm. Leading zeroes may be blank.
Column 50 = Shall contain “Y” to specify the Y location
Column 51 = “+” or “-” or blank to specify the sign (blank = “+”)
Columns 52-57 = Shall contain six digits representing the Y coordinate in 0.0001 Inch or
0.001mm. Leading zeroes may be blank.
Feature Size Field (columns 58-71)
Column 58 shall contain an “X”
Columns 59-62 X - dimension in 0.0001 Inch or 0.001 mm
Column 63 shall contain “Y”
Columns 64-67 Y - dimension in 0.0001 Inch or 0.001 mm
Column 68 shall contain R to signify Counter Clockwise Rotation of feature
Columns 69-71 shall contain 3 digits to represent rotation (000-360)
Column 72 Is unassigned and should be left blank
Soldermask Field (columns 73-74)
Column 73 Shall contain “S” to signify soldermask information
Column 74 = 0  specifies no solder mask
= 1  specified primary side soldermask
= 2  specifies secondary side soldermask
= 3  specifies both sides soldermasked
Alternate Test Point Record  (Columns 75-80)
Column 75 “A” indicates an alternate test record exists
Columns 76-80    A five digit alphanumeric identification representing the alternate test record HEADER INFORMATION
The header information always starts with a “P” in column 1 and two blanks in columns 2-3 , followed by the parameter designation in columns 4-7 , two blanks in columns 8-9 and the value of the paramet
er in column 10-72.
Parameter Description
JOB the name of the job
FORM specify if the format of the IPC-D-356 data is FIXED or VARIABLE
(Note : in this document , only the Fixed format is described)
CODE Indicate a switch to native language character set for comment records
DIM Data Information Module - for netlist data , always “N”
UNITS Units of measurement :
CUST 0  or  CUST    Inches and degrees
CUST 1                      Millimeters and degrees
CUST 2                      Inches and radians
TITLE title of the data defined in this file
NUM part number of the data
REV revision number of the data
LANG data exchange format , usually always “SDEF”
SCALE scale factor of the data
TOL Tolerance specification
LAYER Layer specification
AREA Description of the board’s rectangular boundaries. The coordinates are specified in columns 32-50 (xmin,ymin) and columns 51-70 (xmax,ymax).
IPC-D-356 Sample File
P  JOB        forw_1
P  FORM      FIXED
P  CODE      01
P  DIM          N
P  UNITS      CUST 0
P  TITLE      standard
P  NUM        1000
P  REV            1.00
P  LANG SDEF
P  SCALE    00010000  0
367 - D1250UA00X+008660Y+032725X1250Y0000 S0 367 - D1250UA00X+008660Y+098725X1250Y0000 S0      367 - D1250UA00X+011680Y+060885X1250Y0000 S0 367 - D1250UA00X+011840Y+087275X1250Y0000 S0 367 - D1250UA00X+017000Y+030995X1250Y0000 S0 317NET1 -      MD0079PA00X+013960Y+0
72575X        Y S3 317NET1 -      M  0079PA01X+013960Y+072575X0220Y0000 S3 317NET1 -      M  0079PA08X+013960Y+072575X0220Y0000 S3 317NET1 -      MD0079PA00X+017160Y+071225X        Y S3 317NET1 -      M  0079PA01X+017160Y+071225X0220Y0000 S3 317NET1 -      M  0079PA08X+017160Y+071225X0220Y0000 S3 317NET1 -      MD0079PA00X+018210Y+076375X        Y S3 317NET1 -      M  0079PA01X+018210Y+076375X0220Y0000 S3 317NET1 -      M  0079PA08X+018210Y+076375X0220Y0000 S3 327NET1 -        A01X+027907Y+077727X0500Y0260 S0 327NET1 -        A01X+030607Y+078977X0500Y0260 S0 317NET2 -      MD0079PA00X+011310Y+070775X        Y S3 317NET2 -      M  0079PA01X+011310Y+070775X0220Y0000 S3 317NET2 -      M  0079PA08X+011310Y+070775X0220Y0000 S3 327NET2 -        A08X+012660Y+065725X0300Y0000 S3 327NET3 -        A08X+013660Y+063725X0300Y0000 S3 327NET3 -        A01X+014157Y+063977X0500Y0260 S3 327NET3 -        A01X+026260Y+082225X0200Y0340 S3 327NET3 -        A01X+027407Y+084727X0500Y0260 S3 327NET8 -      M    A01X+012050Y+064477X0400Y0700 S0
NETLIST TRACE DATA FILE  (.NTD)
The following is the specification of the Netlist Trace Data format (NTD). This data file format was creat
ed to accompany an IPC-D-356 data file , and to supply the trace data that the IPC-D-356 file format does not supply.
File Description:
The .NTD file is in ASCII format , comma (,) delimited. The data is in standard ASCII and there is a comma (,) separating each field in the record. The fields are of variable length , and each record in the data file must end with a newline character (either carriage return , or a carriage return/linefeed pair).
Note : due to the fact that the comma (,) is used as the field delimiter , it may not be used in any of the record data.
Basic Data Format :
The data in the .NTD file is stored in the following format :
Data , Type Indicator , Data
The format of the data section  is determined by the Data Type Indicator (DTI).
The DTI codes presently defined are as follows :
Units  - Units of measurement
Comment - Comment or remarks (Not Processed)
Signal - Signal data
Extension - Extension of previous signal data record
ntdLayer - Layer type identification
Sorted  - Indicate if the data is sorted (see below)
Please note that the DTI code appears as the whole word. This is done to allow maximum flexibility and readability of the data file. To reduce the size of the resulting .NTD file , the following DTI codes can be abbreviated as follows :
Comment -    C
Signal - S
Extension -    E
Layer - L
Since Units only appears once per file , as does the Sorted DTI code , they have no need for abbreviation.

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