ArduinoAm29F010

Changeset

20:7c485cb1335c
2015-02-28 Paul Boddie raw files shortlog changelog graph Added dual ROM adapter and other addressing-related notes.
README.txt (file)
     1.1 --- a/README.txt	Tue Jan 20 23:23:33 2015 +0100
     1.2 +++ b/README.txt	Sat Feb 28 19:43:37 2015 +0100
     1.3 @@ -34,7 +34,9 @@
     1.4  Pin 1 in a ROM socket would correspond to A15 but is not necessarily
     1.5  connected, nor, perhaps, is A14 since only 14 bits are required to address 16
     1.6  kilobytes, although there may be 32 kilobyte sockets connecting A14 and using
     1.7 -15 bits to address 32K.
     1.8 +15 bits to address 32K. A16 and A15 would probably be connected to ground to
     1.9 +ensure correct operation, but could also be wired to a selection mechanism so
    1.10 +that the entire contents of the flash memory might be exposed.
    1.11  
    1.12  Pin 28 is a ROM socket would provide power, but the corresponding pin 30 on an
    1.13  Am29F010 is not connected. Thus pin 30 would need routing to pin 32 for the
    1.14 @@ -43,6 +45,31 @@
    1.15  Pin 31 for the Am29F010 would need to be asserted. Thus pin 30 might also be
    1.16  routed to pin 31, so that the device would remain read-only at all times.
    1.17  
    1.18 +Dual ROM Adapter Usage
    1.19 +======================
    1.20 +
    1.21 +A single Am29F010 device could be wired to two ROM sockets in order to provide
    1.22 +data to both. The above wiring guide would be employed, with connections from
    1.23 +both sockets being connected to the Am29F010, but additional logic would be
    1.24 +required for the CS# signals originating from the sockets in order to expose
    1.25 +the appropriate region of flash memory. ROM #1 would be served by a "lower"
    1.26 +16K region; ROM #2 would be served by an "upper" 16K region; A14 would be used
    1.27 +to switch between these regions.
    1.28 +
    1.29 +When ROM #1's CS# signal is low, an attempt to read from ROM #1 would be
    1.30 +occurring, and thus A14 would be held low. And when ROM #2's CS# signal is
    1.31 +low, an attempt to read from ROM #2 would be occurring, and thus A14 would be
    1.32 +held high.
    1.33 +
    1.34 +ROM #1 CS#  ROM #2 CS#  Am29F010 A14
    1.35 +----------  ----------  ------------
    1.36 +0           0           Not defined
    1.37 +0           1           0
    1.38 +1           0           1
    1.39 +1           1           Not defined
    1.40 +
    1.41 +It might therefore be possible to connect A14 to ROM #1's CS# signal.
    1.42 +
    1.43  Pins
    1.44  ====
    1.45