Forum › Category: Layout › How Many Types of Macros Are There in LEF/DEF?
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AvatarCircuitDesigner asked 4 months ago
According to my knowledge there are following types of macros are there in LEF/DEF vlsi technology.
  • COVER Macros
  • RING Macros
  • BLOCK Macros
  • PAD Macros
  • CORE Macros
  • ENDCAP Macros
I don't know the detail or definition of each, if anyone knows, please reply.
3 Answers
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AvatarVLSI Master answered 4 months ago

Nice question for VLSI and Physical design engineer. I know some defination, let me write it here.

COVER Macros

These are fixed to the floorplan and cannot be changed. They're used for things like power routing around the core. You won't find active devices in COVER macros, so they don't impact placers (tools that determine the placement of cells on a chip).

Aslo BUMP is a sub-class of COVER macros, these are physical-only cells with bump geometries and pins, typically found on the top-most metal layer.

RING Macros

These are large macros with an internal power mesh, exposing power-pin shapes forming a ring along the boundary. When you add power stripes across these macros, they connect to the ring but don't go inside it. These macros can also be used for power-switch cells that form a power-ring around a power-domain.

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AvatarDigitalWorld answered 4 months ago
Hello Everyone, i have a definition for following LEF/DEF term. Actually this LEF/DEF play very important role in Physical design and in Layout design.   BLOCK Macros: These are predefined macros used in hierarchical design. They can have sub-classes like:
  • BLACKBOX: Contains only a SIZE statement to estimate its total area. It might include pins, but often these are defined in a Verilog description instead.
  • SOFT MACRO: Contains a version of the sub-block that isn't fully implemented. Parts of it can be modified, unlike BLACKBOX macros which have no sub-block implementation available.
  So, ‘BLOCK’ macros are like predefined building blocks in our design. They serve a hierarchical purpose. Some of them are ‘BLACKBOX’ cells, which might only estimate their area with a SIZE statement. Others are ‘SOFT’ cells, which aren’t fully implemented yet.
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Avatarsemiconductor answered 4 months ago

Nice answers, intresting topic, let me explain following types of macro.

PAD Macros

These are used for input, output, power, and other similar functionalities. For example, a power pad cell might connect to the core power ring and complete the I/O power ring.

CORE Macros

These are the default type if no specific CLASS is defined. They include various types of cells like feedthroughs, tie cells (TIEHIGH, TIELOW), spacers, antenna cells, and well taps.

ENDCAP Macros

These are used to define the end caps in a design and can be specified for different positions such as PRE, POST, TOPLEFT, TOPRIGHT, BOTTOMLEFT, and BOTTOMRIGHT.