From 8434bf85a2f9b219c9b5f872ef3da8afbdd15d97 Mon Sep 17 00:00:00 2001
From: Ben Reynwar <breynwar@isi.edu>
Date: Wed, 4 Aug 2021 17:45:47 -0400
Subject: [PATCH] Adding description of segdata file format.

Signed-off-by: Ben Reynwar <breynwar@isi.edu>
---
 docs/db_dev_process/parts.rst | 37 ++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/docs/db_dev_process/parts.rst b/docs/db_dev_process/parts.rst
index 0ade1566..9e6ef9d9 100644
--- a/docs/db_dev_process/parts.rst
+++ b/docs/db_dev_process/parts.rst
@@ -10,7 +10,7 @@ bitread:
     to get the various FASM features.
 segmatch:
     Used in the fuzzing process to correlate the different bits and find which one belong to which feature.
-gen_part_base_yaml.
+gen_part_base_yaml:
     Used to get a high level information on the device structure (number of
     configuration rows/columns and maximum frame addresses)
 xc7frames2bit:
@@ -24,3 +24,38 @@ bits2rbt:
     ???
 frame_address_decoder:
     ???
+
+segmatch
+--------
+This tools takes input files of the format:
+
+code::
+    seg 00000000_050
+    bit 38_15
+    bit 39_14
+    <....>
+    tag HCLK_IOI3.LVDS_25_IN_USE 0
+    tag HCLK_IOI3.ONLY_DIFF_IN_USE 0
+    <...>
+    seg 00001C80_050
+    bit 38_15
+    bit 38_26
+
+where `seg <base_frame_address> <tile_offset>` indicates how to address the tile,
+and `bit <frame_address_offset> <bit_position>` indicates the position of the bit
+within the tile.
+
+base_frame_address:
+  The frame address of the first frame that configures the tile.
+
+tile_offset:
+  The word index of the first word that configures the tile within a frame.
+
+frame_address_offset:
+  frame_address - base_frame_address
+
+bit_position:
+  The index of the bit within the words of this frame that configure this tile.
+
+The `prjxray.segmaker.Segmaker` is a helper class that can be used to write these
+files inside the fuzzer's `generate.py`.