# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1435877634 -7200
# Node ID e83106388811daa4d9ec739b3e561e62a4b7a24a
# Parent  d6482c4f3bb2645ef2b2baf7fb3da554ff68027d
Expanded the documentation, giving notes about testing and sector access.

diff -r d6482c4f3bb2 -r e83106388811 README.txt
--- a/README.txt	Mon Mar 09 01:03:39 2015 +0100
+++ b/README.txt	Fri Jul 03 00:53:54 2015 +0200
@@ -20,6 +20,9 @@
 
 sudo make upload
 
+Testing the Program
+-------------------
+
 With the program uploaded, it should now be possible to communicate with the
 Arduino. Unless the programming circuit has been constructed, however, there
 will not be any effect of communicating with the Arduino, other than to check
@@ -37,6 +40,14 @@
 various commands. Merely getting the prompt should be enough of an indication
 that the program is functioning on the device.
 
+Issuing read commands permits the testing of addresses in the device:
+
+R0000 (reads from the first location, 0x0000, residing in sector 0)
+R7fff (reads from the final location, 0x7fff, residing in sector 3)
+
+Uploading and Testing Images
+----------------------------
+
 Once the programming circuit has been constructed (see "Arduino Interfacing"
 below), the upload.py script can be used to upload data to the Am29F010
 device. For example:
@@ -63,6 +74,16 @@
 individually, especially if the circuit is behaving in a less than completely
 reliable fashion.
 
+A Note on Sectors
+-----------------
+
+Each sector is 16 kilobytes long, which corresponds to a 14-bit address range
+(0x0000 to 0x3FFF). The Arduino interface described below supports 16-bit
+addressing (A0...A15), permitting access to four sectors (at 0x0000, 0x4000,
+0x8000 and 0xC000), leaving A16 grounded and thus not accessing the upper four
+sectors in the device. However, A16 could be connected to VCC to access the
+upper four sectors.
+
 Device Compatibility
 ====================
 
@@ -180,6 +201,11 @@
 GND                     A16
 GND                     GND
 
+Note that A15 and A16 are left grounded, effectively exposing only the first
+two sectors of the device. By connecting either or both of these to VCC, other
+pairs of sectors can be manually selected. A mechanism could also be devised
+to allow selection using logic, but this is not explored here.
+
 Arduino Interfacing
 ===================