diff --git a/README.md b/README.md
index d30a9de..271c84d 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,8 @@ There is 64KB of memory and this is broken into
 
 Resolution of the "attached display" is 64 * 64, so 4096 bytes.  Each "pixel" is blown up to be 8 pixels in size so things are nice and blocky.  
 
+Writing a byte to 0xE000 will draw a pixel at the top left and at byte at 0xF000 will display at the bottom right.
+
 Each pixel can be one of 256 colours where bits:
 
 * 0-1 are blue  
@@ -51,6 +53,8 @@ Each pixel can be one of 256 colours where bits:
 
 The last key pressed is stored to 0xF001 and it's up to your programs to clear this out after reading if you don't want to repeatedly read the same keypress.
 
+SDL is used for reading key presses and the code for each key is https://wiki.libsdl.org/SDLScancodeLookup.  Only key presses where the code is <= 0xFF are logged.
+
 ## Sample
 
 The _sample/draw.s_ file contains well commented 6502 assembly code for a simple program which allows you to draw multi-coloured lines with your cursor keys.  What fun!