Using IPC-D356 to Import Nets and Nodes
Since Gerber data has no net or node information, the output from NETEX-G will not include the net names and node (or pin) names assigned by the board designer. However if the simulation engineer is provided with an IPC-D-356 file by the board designer, then this file can be imported by NETEX-G and net names and pin names can be extracted from it.
What is IPC-D-356?
IPC356 is a file format specification created by the IPC that defines test points on a board and is used to create test programs and test fixtures for the PCB. It is in ASCII column format and includes net names, pin and reference designators, coordinates and type of test point. Most PCB design software can export this file as it is very useful and requested by the PCB manufacturer. The original IPC356 has been updated so that there is both IPC356A and B versions in use. NETEX-G can read either version. A sample is shown below:
P  JOB   BPN 710064-0001
P  UNITS CUST 0
P  VER IPC-D-356A
P  IMAGE PRIMARY

317+3.3V            J13   -2    D0400PA00X+043550Y+006480
327+3.3V            C171  -1          A01X+041900Y+006660
327+3.3V            D1    -3          A08X+040650Y+007720
317BSP_R0_B5        VIA         D0098PA00X+023895Y+022535
327BSP_R0_B6        R335  -1          A08X+024140Y+022050
327BSP_R0_B6        U26   -35         A01X+030400Y+019515
327BSP_R0_B6        R334  -1          A08X+023733Y+022050
327GND              C215  -2          A08X+050850Y+047799
327GND              C415  -2          A08X+025278Y+008183
327PCI_CLK          J1A1  -25         A01X+028198Y+000600
327PCI_CLK          U26   -46         A01X+030715Y+015735
999
Generally speaking, the test points defined by IPC-D-356 are either on the top or bottom of the PCB. In this example, A01 is the first layer and A08 is the bottom layer. The first 3 characters define the type of test point, followed by the net name. You can see the reference designator information followed by a pin number for components. You can also see a via which has no ref designator or pin but for which the pad size is described.
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