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docs/source/routing.md

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