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Amstrad CSD

1,112 bytes added, 09:36, 1 August 2012
/* The CSD System Cartridge */
Lots of information is not known at this time.
It uses ports fbe0-fbe3. The exact decoding and operation of these ports is unknown.
fbe0 This port is read only it seems. bits 7..4 seem to be related to the dip switches on the CSD with bit 7 seems to be fixed to GND/0v.
bit 6,5 is the timer value. It is the time allowed between choosing next cartridge to play.
bit 6, bit 5
 
off off = 8 1 1
off on = 16 1 0
on off = 24 0 1
on on = 32 0 0
 
bit 4 seems to be timer on/off for time limited play.
fbe0 bits 3..0 are defined by the dial
bit 3 is ignored.
bit 6, bit 5
off off = 8s 1 1
off on = 16s 1 0
on off = 24s 0 1
on on = 32s 0 0
bit 4 seems to be timer on/off for time limited play.
bits 3..0 are defined by the dial
bit 3 is ignored.
0 = forever?
1 = 8s,
2 = 56s
fbe2 is read only it seems
bits 7..3 are the currently selected cartridge
bits 3..0 ???
fbe1 is writeable
bits 7,6: ???
bits 5..0: are cartridge number??
fbe3 is writeable:
bits 7..4: are cartridge number
bits 3..0: ???
 
== The CSD System Cartridge ==
 
The system cartridge uses the following plus features:
* sprites
* palette
* raster interrupts
 
The software reads each of the 12 slots to determine if there is a cartridge installed. It also looks for a specific header which can be recreated with the following code:
fbe2 org &0000 start: ;; a standard cartridge is read only it seemsexecuted here when inserted intobits 7 ;; a CPC+..3 are jp start1 ;; a JP instruction at &0000 defb "AMS" ;; this is the currently selected cartridgeimportant identificationbits 3..0 ??? jp start2 ;; a JP instruction at &0006 jp start3 ;; a JP instruction at &0009 start1: ld bc,&7f00 out (c),c ld bc,&7f4f out (c),c jp start1 start2: ld bc,&7f00 out (c),c ld bc,&7f4b out (c),c jp start2 start3: ld bc,&7f00 out (c),c ld bc,&7f40 out (c),c jp start3 end start
Offset 0 is the normal execution point for cartridges when run on GX4000 and Plus.
fbe1 It is writeable bits 7believed the others are for a rolling demonstration mode,6: ???bits 5and a play mode that is limited..0: are cartridge number??
fbe3 The only cartridge to have this header is writeable:bits 7..4: are [[Pang (cartridge numberbits 3.)|Pang]].0: ???
== Pictures ==
Arnoldemu
2,541
edits
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