diff --git a/sd/README.md b/sd/README.md
index d533dad..bbefafc 100644
--- a/sd/README.md
+++ b/sd/README.md
@@ -58,6 +58,11 @@ BA58ED29,716956B4,4E45531A100010080000070700000001
 Name    
 CRC32 (prg+chr combined), CRC32 (512 bytes), iNES Header   
 
+## nes20db.txt  
+This file stores NES 2.0 data about NES ROMs, generated from [NewRisingSun's nes20db XML file on NesDev](https://forums.nesdev.org/viewtopic.php?t=19940).  Converting updated versions of the XML file to this format requires compiling and running [NES20Tool](https://github.com/Kreeblah/NES20Tool) with the following options at runtime:
+
+    NES20Tool -operation transform -xml-file nes20db.xml -xml-format nes20db -format-transform-type sanni -format-transform-destination nes20db.txt
+
 ## snes.txt    
 This file is needed for odd sized SNES games like Final Fantasy (JAP), Super Metroid(US/JAP) or Tales of Symphonia. Without this file you will get overdumps and the checksum calculation will fail.    
 
@@ -69,4 +74,4 @@ Name
 CRC32, internal checksum, size in Mbit, number of banks (lorom needs twice as many banks as hirom for the same rom size, lorom: 32kb banks, hirom: 64kb banks)    
 
 ## snes_clk.txt    
-Calibration data for clock generator.     
+Calibration data for clock generator. Generated by the cartreader calibration function.