Multiple IO Ring

Creating Multi I/O Ring Die

Using IC Compiler

Sufyan Khan, Synopsys Inc.

John Ho, Synopsys Inc.

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As feature sizes continue to shrink, die sizes are more often becoming pad limited

Single perimeter ring of required I/Os is larger than core required to implement functions of the chip

The Problem: Pad Limited Design

core

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Fit concentric I/O rings around required core size

Innermost ring is usually segmented

The Solution: Multiple I/O Rings

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Flow

IC Compiler

Design Planning Flow

Read Netlist

Virtual Flat Placement

Multiple I/O Planning

Set Pad Physical Constraints

Create Initial Floorplan

Create Blockages

Create Floorplan (Boundary Ctrl)

Manual Adjusted Placements

Fix IO Placements

Insert IO Filler Cells

Remove Blockages

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Create Blockages



Fix IO Placements


Remove Blockages

Minimum input data: Total number of rings Ring number for each IO Side number for each IO

Use set_pad_physical_constraints command to define IO constraints

Use -chip_level_ring option to specify the total ring number

Use -ring option to set ring number for each IO

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Create Blockages



Fix IO Placements


Remove Blockages

Example:

set_pad_physical_constraints \

-chip_level_ring {depth 2}


-pad_name PAD_1 -ring 1 -side 3 -order 5





PAD_1

PAD_2 PAD_3

Note: Up to 6 levels of rings are

supported

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Change Pad Orientation



Create Blockages



Fix IO Placements


Remove Blockages

Use

set_pad_physical_constraints

command and following options to

change orientation for four sides -lib_cell -pad_name string

-lib_cell_orientation {L T R B}

The string for pad_name is a cell reference name if lib_cell is used

The setting of {L T R B} is an

additional rotation for left, top, right,

and bottom sides of floorplan. It can be set as N, W, S, E, FN, FW, FS, or FE.

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N rotate 0




Create Blockages



Fix IO Placements


Remove Blockages

W rotate 90

S rotate 180

E rotate 270

FN mirror X

FS mirror Y

FW rotate 90 first and then mirror X

FE rotate 90 first and then mirror Y

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-lib_cell \

-pad_name F_CELL \

-lib_cell_orientation {W S N S}



Create Blockages



Fix IO Placements


Remove Blockages

F

F F

F

F

F F

F

Example

Initial Orientation After Rotation

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Spacing Between IO Rings

You can specify the spacing between the rings using set_inter_io_ring_spacing

command

IC Compiler allows to set the inter ring spacing per side based

-left_ring_spacing

-top_ring_spacing

-right_ring_spacing

-bottom_ring_spacing



Create Blockages



Fix IO Placements


Remove Blockages

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Spacing Between IO Rings

Example:

set_inter_io_ring_spacing \

-ring 1 \

-left_ring_spacing 40 \

-top_ring_spacing 30 \

-right_ring_spacing 20 \

-bottom_ring_spacing 10



Create Blockages



Fix IO Placements


Remove Blockages

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10

40

20

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Use create_floorplan

to create the initial floorplan and place

the IO cells

Example:

create_floorplan \

-core_utilization 0.7 \

-core_aspect_ratio 1.2



Create Blockages



Fix IO Placements


Remove Blockages

NOTE:

Please migrate all scripts using initialize_floorplan to create_floorplan

command. Synopsys plans to retire initialize_floorplan command

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Create Blockages



Create Blockages



Fix IO Placements


Remove Blockages

User can use create_placement_blockage

to reserve the space in I/O ring areas

IO pads are still overlapped with blockages after blockages are created

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Create Blockages



Create Blockages



Fix IO Placements


Remove Blockages

Example:

create_placement_blockage \

-coordinate {{x1 y1}{x2 y2}} \

-name placement_blockage_1 \

-type hard




-type hard

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Create Floor Plan Boundary Control



Create Blockages



Fix IO Placements


Remove Blockages

Use command

create_floorplan \

-control_type boundary

to honors the placement blockages

You can also use following options to set the distance between the core and the pad cells

-left_io2core distance

-top_io2core distance

-right_io2core distance

-bottom_io2core distance

NOTE:

(1) If a distance is a negative value, the boundary

of core area will beyond pads (2) Option -min_pad_height is replaced by

these -*_io2core options

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Create Blockages



Fix IO Placements


Remove Blockages

Example:

create_floorplan -control_type boundary \

-left_io2core -80 \

-top_io2core -80 \

-right_io2core -80 \

-bottom_io2core -80

-80

-80

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Create Blockages



Fix IO Placements


Remove Blockages

You can manually place IO Macros locations by using GUI in layout view

IO Macro

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Fix Placement and Insert IO Filler



Create Blockages



Fix IO Placements


Remove Blockages

After IO cells location are refined and fixed, its time to insert filler cells

Perform automatic filler cell insertion using insert_pad_filler ring

option specifies which ring fillers will be

placed

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Remove Blockages



Create Blockages



Fix IO Placements


Remove Blockages

You can remove the placement

blockages

Open spaces in the internal IO ring may be used for standard cell placement

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Case Study

VDDIO_2

Multi-height

I/Os

IOs in

Core Area

Pad

Filler

I/O

Macros

Corner

Cells

VDDIO_1

Multiple

I/O Power

Domains

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Create Initial Floor Plan

# Rings and spacing


-chip_level_ring {{depth 2}}

set_inter_io_ring_spacing \

-ring 1 \

-left_ring_spacing 100 \

-top_ring_spacing 100 \

-bottom_ring_spacing 100 \

-right_ring_spacing 100

source io_constraints.tcl

# Create Initial Floorplan

create_floorplan

Multi-height

I/Os

Power

Break Cell

Corner

Cells

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Create Placement Blockages

# Add placement blockages




-type hard




-type hard

Placement

Blockage

Placement

Blockage

Overlapped

with IO

Pads

Placement

Blockage

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# create floorplan with

# boundary control

create_floorplan \

-control_type boundary \

-top_io2core -310\

-bottom_io2core -264 \

-left_io2core -100 \

-right_io2core -467

Placement

Blockage

Core Area

Placement

Blockage

Placement

Blockage

IO Pads are

Relocated

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Manual Adjusted Placement

IO

Macro IO

Macro

# Place IO macros

set_attribute \

-quiet IOMACRO_INST1 \

origin { 638.850 2520.000}

set_attribute \

-quiet IOMACRO_INST2 \

origin {4061.320 2520.000}

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Fix I/O Placement and

Insert I/O Filler Cells

Pad

Fillers

# Add IO fillers

insert_pad_filler \

-ring 1 -cell \

"FILLER55 FILLER40 FILLER35 \

FILLER20 FILLER15 FILLER10 \

FILLER5 FILLER1 FILLER01

insert_pad_filler \

-ring 2 -cell \

"FILLER55 FILLER40 FILLER35 \

FILLER20 FILLER15 FILLER10 \

FILLER5 FILLER1 FILLER01"

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Limitations

When placing IOMACROs or multi-height IOs in the IO ring the adjacent side leaves some gaps

to align with the height of the taller IOs

Use placement blockage flow for IOMACROs

Manually adjust some IO placement to fill the gap

Create_floorplan does not support Rectilinear floorplans at this time for Multi-IO Rings.

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Summary

IC Compilers multiple I/O ring flow helps designers solve pad limited design challenges Minimize die sizes as required by core density versus being

limited by a single pad ring

We demonstrated how to create a complex, multi-ring IO structure, including: multi-height I/O cells I/O macros multiple I/O power domains

IC Compiler supports multiple I/O rings starting from the F-2011.09 release

Multiple IO Ring

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