# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1421792217 -3600
# Node ID 191fa5092e13924e6eda96e0713aae241660529d
# Parent  53799b196670beb210b563e326bf6d430ef0a57f
Added a device compatibility section and tidied up the Arduino wiring details.

diff -r 53799b196670 -r 191fa5092e13 README.txt
--- a/README.txt	Tue Jan 20 22:51:05 2015 +0100
+++ b/README.txt	Tue Jan 20 23:16:57 2015 +0100
@@ -1,6 +1,48 @@
 The Am29F010-90PC product has been used to test the software and hardware
 design described here.
 
+Device Compatibility
+====================
+
+For use with an Acorn Electron ROM cartridge or other board providing a ROM
+socket, the compatibility of the Am29F010 needs to be assessed in the context
+of the ROM sockets likely to be provided.
+
+Original ROM Pinout     Am29F010 Pinout
+-------------------     ---------------
+
+                             1  \/  32 VCC
+                        A16  2      31 WE#
+     1  \/  28 VCC      A15  3      30
+A12  2      27 A14      A12  4      29 A14
+A7   3      26 A13      A7   5      28 A13
+A6   4      25 A8       A6   6      27 A8
+A5   5      24 A9       A5   7      26 A9
+A4   6      23 A11      A4   8      25 A11
+A3   7      22 OE#      A3   9      24 OE#
+A2   8      21 A10      A2  10      23 A10
+A1   9      20 CS#      A1  11      22 CE#
+A0  10      19 D7       A0  12      21 DQ7
+D0  11      18 D6       DQ0 13      20 DQ6
+D1  12      17 D5       DQ1 14      19 DQ5
+D2  13      16 D4       DQ2 15      18 DQ4
+GND 14      15 D3   GND/VSS 16      17 DQ3
+
+Superimposing the Am29F010 onto a ROM socket would provide compatibility for
+all pins from A12 to GND/VSS and from A14 to D3/DQ3.
+
+Pin 1 in a ROM socket would correspond to A15 but is not necessarily
+connected, nor, perhaps, is A14 since only 14 bits are required to address 16
+kilobytes, although there may be 32 kilobyte sockets connecting A14 and using
+15 bits to address 32K.
+
+Pin 28 is a ROM socket would provide power, but the corresponding pin 30 on an
+Am29F010 is not connected. Thus pin 30 would need routing to pin 32 for the
+flash device socket.
+
+Pin 31 for the Am29F010 would need to be asserted. Thus pin 30 might also be
+routed to pin 31, so that the device would remain read-only at all times.
+
 Pins
 ====
 
@@ -115,14 +157,14 @@
 A3                                  WE#
 2           CP
 3                       CP
-4           D0 (*)      D0 (*)      DQ0
-5           D1 (*)      D1 (*)      DQ1
-6           D2 (*)      D2 (*)      DQ2
-7           D3 (*)      D3 (*)      DQ3
-8           D4 (*)      D4 (*)      DQ4
-9           D5 (*)      D5 (*)      DQ5
-10          D6 (*)      D6 (*)      DQ6
-11          D7 (*)      D7 (*)      DQ7
+4           D0          D0          DQ0
+5           D1          D1          DQ1
+6           D2          D2          DQ2
+7           D3          D3          DQ3
+8           D4          D4          DQ4
+9           D5          D5          DQ5
+10          D6          D6          DQ6
+11          D7          D7          DQ7
             Q0                      A0
             Q1                      A1
             Q2                      A2
@@ -140,16 +182,10 @@
                         Q6          A14
                         Q7          A15
 GND                                 A16 (not used)
-5V          MR# (**)    MR# (**)
+5V          MR#         MR#
 5V          VCC         VCC         VCC
 GND         GND         GND         VSS
 
-(*) Apply pull-down resistor to 74HC273 D inputs when driving using switches.
-(**) Apply pull-up resistor to 74HC273 MR# inputs to preserve state.
-
-74HC273 Q outputs may initially be high and should be reset, either driving
-MR# low or by explicitly latching values onto each device.
-
 Set Address
 -----------