Add support for BANKED on cpc

[poppichicken]

hi Marco.

Has BANKED been implemented on CPC?
This doesn't compile:

 BITMAP ENABLE(320,200,4)
 COLOR BORDER WHITE
 CLS BLACK
 DEFINE KEYBOARD ASYNC

 player:=LOAD IMAGE("image/airplane.png") BANKED

This makes sense if you're only targeting the 464 and 664 models, of course.

[spotlessmind1975]

Hi @poppichicken , and thank you for your bug report!

Support for memory expansions is not yet available on cpc, but is being implemented. The real problem, at the moment, would be to introduce data loading at startup. In fact, the current implementation on other targets requires that the memory expansion is loaded with data prepared by the compiler at startup. This step must be implemented to implement commands like LOAD IMAGE.

I convert this ticket.

[poppichicken]

Ah, I see.
Thanks.

[spotlessmind1975]

I am going to use the explanation here:
https://cpcrulez.fr/applications_util-bankrsx-amstrad_action.htm

[spotlessmind1975]

From a first analysis, the main problem lies in the fact that the memory area for banking is located "in the middle" of the executable, in the range 0x4000 - 0x7fff. As of today, the executable can theoretically have 48895 bytes. Limiting the extension to the address 0x3fff, we would have an executable of a maximum of only 16127 bytes (and it would only be a gain for the 6128, because the 464/64 has nothing to bank switch with!). The code generator could be modified to move the data memory from address 0x8000 onwards, and move all the included libraries up.

In summary, it will be necessary to differentiate the generation of executables for 464/664 and 6128, so that the latter has a different generator of executables, capable of dislocating the memory differently, and thus leaving the identified window free.

Once this is done, a special routine at boot will load from disk into the (sequential) memory banks switched from time to time.

Qui di seguito lo pseudocodice individuato per il cambio dei banchi:

 #define crBANKSetC0( ) asm( "ld bc, $7f00 \n out (c), c \n ld a, $C0 \n out (c),a" );
 #define crBANKSetC4( ) asm( "ld bc, $7f00 \n out (c), c \n ld a, $C4 \n out (c),a" );
 #define crBANKSetC5( ) asm( "ld bc, $7f00 \n out (c), c \n ld a, $C5 \n out (c),a" );
 #define crBANKSetC6( ) asm( "ld bc, $7f00 \n out (c), c \n ld a, $C6 \n out (c),a" );
 #define crBANKSetC7( ) asm( "ld bc, $7f00 \n out (c), c \n ld a, $C7 \n out (c),a" );

[poppichicken]

That all makes sense.
It will be a great feature.
:)