constraints module

Design-rule Tag subclasses and antipad fence-via rules for the BGA escape design.

StriplineDiffPairTag keys the 85 ohm differential routing structure rule (built in bga_escape.BGALink, which owns the GND reference net); the antipad fence tags key the per-layer fence-via rules defined at the bottom of this file.

JITX discovers DesignConstraint rules by walking the design object tree, so a module-level rule takes effect only once it is reachable from the design — the rules here are anchored as attributes of substrate.BGAEscapeSubstrate.

class StriplineDiffPairTag

Bases: Tag

85 ohm differential stripline trunk net.

Carries the differential routing structure via a tag rule (see BGALink), so the diff pairs get their impedance-controlled cross-section without an explicit >> topology or a far-end terminal.

class AntipadFenceTag

Bases: Tag

Signal-via antipad GND pour on L7 (Ground4), fenced by uGnd_L1_L7.

Upper-reference-plane antipad fence around the BGA wave-port launch of any Signal4-deskew row pair.

class Ground3AntipadFenceTag

Bases: Tag

Signal-via antipad GND pour on L5 (Ground3), fenced by uGnd_L1_L5.

class Ground2AntipadFenceTag

Bases: Tag

Signal-via antipad GND pour on L3 (Ground2), fenced by uGnd_L1_L3.

class DeskewAntipadFenceTag

Bases: Tag

Deskew antipad GND pour on L9 (Ground5), fenced by uFence_L7_L9 (the Signal4 stripline-reference fence via).

class Ground4DeskewAntipadFenceTag

Bases: Tag

Deskew antipad GND pour on L7 (Ground4), fenced by uFence_L5_L7.

class Ground3DeskewAntipadFenceTag

Bases: Tag

Deskew antipad GND pour on L5 (Ground3), fenced by uFence_L3_L5.

class Ground2DeskewAntipadFenceTag

Bases: Tag

Deskew antipad GND pour on L3 (Ground2), fenced by uFence_L1_L3.