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Vortex Expansions RAM card

1,051 bytes added, 19:44, 28 February 2010
/* Manual */
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== Technical (very incomplete) ==
 
* This section describes how you can access the RAM of the SP512.
* The exact decoding (e.g. complete or partial) of I/O port addresses is not confirmed at this time.
* The port addresses given are recommended and are those used by B.O.S..
 
I/O port &FBBD:
Bit Function
7 Unknown
6 Unknown (Discology utility uses it - does it choose RAM in 32K blocks instead of 64K blocks??)
5 When 1, bits 2..0 define which 64k block of SP512 RAM to select. When 0, chooses internal 64K RAM of CPC464.
4 Unknown
3 Unknown
2..0 Used to choose the 64K block of the SP512 to select
 
I/O port &7F00:
Bit Function
7 Set to 1
6 1 = make RAM visible in range &8000-&FFFF, 0 = make RAM visible in range &0000-&7FFF
5 Set to 1 to activate SP512. If bit 5 of &FBBD is 1 will select SP512 ram, otherwise select RAM of CPC464.
3 1 = Upper ROM disable, 0 = Upper ROM enable
2 1 = Lower ROM disable, 0 = lower ROM enable
1,0 Screen mode
 
* When bit 5 is 0, then bit 6 is ignored.
* When reading, ROM has priority over the RAM.
== Manual ==
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