diff --git a/README.md b/README.md
index 6505958..ff5afa1 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,31 @@ Using the premade files will have the 13-sector image loaded when jumpers on J1
 
 ### Configuring the address
 
-**TODO**
+The address for the I/O ports (DEVICE SELECT) can be changed by jumpering J3.
+
+```
+J3: DEVICE SELECT
+
+C C C C C C C C
+0 0 0 0 0 0 0 0
+8 9 A B C D E F
+x x x x x x x x
+  ^ default
+```
+
+The address for the ROM (I/O SELECT... confusing, I know) can be set by jumpering J2.
+
+```
+J2: I/O SELECT
+
+C C C C C C C C
+1 3 5 7 9 B D F
+x x x x x x x x
+x x x x x x x x
+^ default
+```
+
+The defaults are marked on the board.
 
 ### Ordering the boards