mirror of https://github.com/VLSIDA/OpenRAM.git
57 lines
1.9 KiB
Markdown
57 lines
1.9 KiB
Markdown
### [Go Back](./index.md#table-of-contents)
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# Routing
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This page of the documentation explains the routing of OpenRAM.
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## Table of Contents
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1. [Power Supply Options](#power-supply-options)
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1. [Power Routing](#power-routing)
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1. [Power Supply Algorithm](#power-supply-algorithm)
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1. [Channel Router](#channel-router)
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## Power Supply Options
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* Unrouted
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* Leave must-connect metal 3 pins for vdd and gnd within the array
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* Grid
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* Connect in a metal 3 and 4 grid
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* Blockage aware
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* Can encounter DRC errors with off-grid pins
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* Works with commercial tools but not so well with OpenRoad
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* Work in Progress: Hanan Grid / Steiner Tree:
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* Route tree on Hanan metal 3 and 4 grid instead of full grid
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* Blockage aware
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## Power Routing
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<img align="right" height="200" src="../assets/images/routing/power_routing.png">
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* All power pins are brought to M3 and routed as a grid on M3/M4
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* Considers blockages of M3/M4 by control and data signals
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* Considers wide/long metal spacing rules
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## Power Supply Algorithm
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* 1st: Route vertical and horizontal grids (blockage aware, allow connection to correct supply)
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* 2nd: Check direct overlaps of power pins
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* 3rd: Single direction probes to connect
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* 4th: A* maze router
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## Channel Router
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* SRAMs typically try to use minimal layers of metal
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* Primarily used to connect decoders, input/output circuitry, or control logic
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* Wish list
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* Minimize number of tracks
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* Must consider impact on floorplan
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| <img height="200" src="../assets/images/routing/channel_router_book.png"> | <img height="200" src="../assets/images/routing/channel_router_connection.png"> |
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| :-------------------------------------------------------------------------: | :---------------------------------------------------------------------: |
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| Credit: Chen & Chang, EDA Handbook, Chapter 12, Global and detailed routing | Sense amp to data flop connection |
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