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title: add_pdn_ring(2)
date: 24/09/08
---
# NAME
add_pdn_ring - add pdn ring
# SYNOPSIS
add_pdn_ring
-layers layer_name
-widths width_value|list_of_2_values
-spacings spacing_value|list_of_2_values
[-grid grid_name]
[-core_offsets offset_value]
[-pad_offsets offset_value]
[-add_connect]
[-extend_to_boundary]
[-connect_to_pads]
[-connect_to_pad_layers layers]
[-starts_with POWER|GROUND]
[-nets list_of_nets]
[-ground_pads pads]
[-power_pads pads]
# DESCRIPTION
The `add_pdn_ring` command is used to define power/ground rings around a grid region.
The ring structure is built using two layers that are orthogonal to each other.
A power/ground pair will be added above and below the grid using the horizontal
layer, with another power/ground pair to the left and right using the vertical layer.
Together these 4 pairs of power/ground stripes form a ring around the specified grid.
Power straps on these layers that are inside the enclosed region are extend to
connect to the ring.
Example usage:
```
add_pdn_ring -grid main_grid -layer {metal6 metal7} -widths 5.0 -spacings 3.0 -core_offset 5
```
# OPTIONS
`-layers`: Specifies the name of the layer for these stripes.
`-widths`: Value for the width of the stdcell rail.
`-spacings`: Optional specification of the spacing between power/ground pairs within a single pitch. (Default: pitch / 2).
`-grid`: Specifies the name of the grid to which this ring defintion will be added. (Default: Last grid created by `define_pdn_grid`).
`-core_offsets`: Value for the offset of the ring from the grid region.
`-pad_offsets`: When defining a power grid for the top level of an SoC, can be used to define the offset of ring from the pad cells.
`-add_connect`: Automatically add a connection between the two layers.
`-extend_to_boundary`: Extend the rings to the grid boundary.
`-connect_to_pads`: The core side of the pad pins will be connected to the ring.
`-connect_to_pad_layers`: Restrict the pad pins layers to this list.
`-starts_with`: Specifies whether the first strap placed will be POWER or GROUND (Default: grid setting).
`-nets`: Limit straps to just this list of nets.
# ARGUMENTS
This command has no arguments.
# EXAMPLES
# SEE ALSO
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