Forward annotation is the process of updating a layout to reflect changes made in the schematic. This process is used when, for example, a new component is added to a schematic and needs to be included in the layout. This section describes how to forward annotate changes in a Lepton schematic to a PADS PowerPCB layout.
PADS implements forward annotation through the use of an ECO (Engineering Change Order) file. The ECO file describes the differences between a current design and the desired design. PADS generates the ECO file by performing a netlist comparison between a new netlist file and the netlist contained in the current layout.
This procedure assumes you have a board layout open in PADS and that
you have made your schematic changes in lepton-schematic
. For the purposes
of illustration, assume your schematic is split into two pages in the
files pg1.sch and pg2.sch.
lepton-netlist -g pads -o mynet.asc pg1.sch pg2.sch
This will create the netlist file mynet.asc.
original design to compare | use current PCB design |
new design with changes | mynet.asc |
√ | generate differences report |
√ | generate eco file |
comparison options | |
√ | compare only ECO registered parts |
attribute comparison level | |
√ | ignore all attributes |
Click the ‘OK’ button to create the ECO file.