Opening Screens in cc65

[TGB1718]

I'm opening a screen (Antic mode 1) using a combination of cc65 and ca65 modules.

Initially I tried _graphics(17) and wrote a text string to the screen using CIO in a .s module channel #6,

this didn't produce anything on the screen.

 

I decided to open the screen in the assembler module, so closed #6, then opened channel 6, then using

channel 6 wrote to the screen again using channel 6 and it works fine.

 

Here's the problem, I need to reserve some memory at the top of RAM, so did the usual get the

value of location 106 ($6A), subtracted 14 from the value and stored the value back to 106.

 

Then I opened the screen and now the text does not appear on screen as before.

 

I have tried all sorts of different values to reserve, but it appears that any lowering of RAM prevents

the output to the screen.

 

I wrote a small routing in MAC/65 to test the code and it works fine with or without the RAM reduction.

 

So my question:- is there something I'm not aware of that cc65/ca65 needs to prevent this from happening,

doesn't really make sense that it doesn't work when the only difference is the lowering of RAMTOP.

 

Any help appreciated

 

void main(void)

{

    POKE(RAMTOP,PEEK(RAMTOP)-14);

    INDEX=gr7;
    opench(); // GRAPHICS 17 OPEN

    printscreen2();

    while(1);

}

 

this is the ca65 open routine

 

   .proc _opench: near
   .code
   LDA #CLOSE ; close channel first
   STA ICCOM,X
   JSR CIOV
   LDX #$60
   LDA #OPEN
   STA ICCOM,X
   LDA # <_NAME
   STA ICBAL,X
   LDA # >_NAME
   STA ICBAH,X
   LDA #$0C    ; RW
   STA ICAX1,X
   LDY _INDEX
   LDA MODE,Y  ; GR.7/GR.8
   STA ICAX2,X
   JSR CIOV
   STY _retcode
   RTS
   .endproc
   MODE:    .BYTE 1,2
   _INDEX:  .BYTE 0

   _NAME: .BYTE "S:\n" 

 

and the print module

    _print6:
          LDX #$60 ; channel 6 opened by _graphics statement
      LDA _POINTER
      STA ICBAL,X
      LDA _POINTER+1
      STA ICBAH,X
      LDA #PUTREC
      STA ICCOM,X
      LDA #40 ; Max line length
      STA ICBLL,X
      LDA #0
      STA ICBLH,X
      JSR CIOV
      STY _retcode
      RTS
    .endproc
_retcode: .byte 0  ; return code
_BUFF:    .res 50   ; line buffer
_POINTER: .word 0

 

[sanny]

> I have tried all sorts of different values to reserve, but it appears that any lowering of RAM prevents

the output to the screen.

 

How did you reserve the memory?

[baktra]

Hello,

 

you should know that the _graphics() function returns the actual IOCB number used to open the S: device.
It is not guaranteed to be IOCB #6 (like in Atari BASIC)

 

To reserve a piece of memory, you will need to use your own ld65 linker configuration file. Changing RAMTOP is of course honored by the Atari OS and Atari BASIC, but not by the C runtime library.

 

For more details, refer to the atari.cfg linker configuration file (look for the RESERVED_MEMORY symbol), and to the cc65-source/libsrc/atari/crt0.s to see how important memory layout related pointers are initialized before your main() starts.

And of course here to see the description of the memory layout.

 

[TGB1718]

@baktra thanks for the info, I'll look into it

[TGB1718]

1 hour ago, baktra said:

you should know that the _graphics() function returns the actual IOCB number used to open the S: device.

Sort of, it returns '3', so I used this as the channel to print to, still nothing, I did an open _graphics(1) so it had

the text box and my print data went there, so I assumed there must be 2 open channels, as it returned 3, I tried 2,

no joy, so I tried 1 and hey presto my text appears, not sure I could rely on that happening every time though.

 

Still have to try the config file to reserve memory

[baktra]

1 hour ago, TGB1718 said:

Sort of, it returns '3', so I used this as the channel to print to, still nothing, I did an open _graphics(1) so it had

the text box and my print data went there, so I assumed there must be 2 open channels, as it returned 3, I tried 2,

no joy, so I tried 1 and hey presto my text appears, not sure I could rely on that happening every time though.

 

Still have to try the config file to reserve memory

I am sorry. I was wrong.

The _graphics() function doesn't return IOCB number but a file descriptor (fd).

Therefore printing should be done as follows:

 

#include <atari.h>
#include <unistd.h>

int main() {
    int fd = _graphics(2);
    write(fd,"hello",5);
    while(1);
    return 0;
}

 

 

[sanny]

On 12/13/2020 at 5:27 PM, baktra said:

To reserve a piece of memory, you will need to use your own ld65 linker configuration file.
 

 

Not really.

You can use

cl65 -t atari -Wl "-D__RESERVED_MEMORY__=0x2000" ...

 

[sanny]

I suggest to read the documentation: https://cc65.github.io/doc/atari.html

[TGB1718]

@sanny thank you, I was looking at the config file, but was having a bit of trouble making sense

of it as the examples didn't really cover what I wanted, this may be a better way

 

[Mariano DM]

On 12/13/2020 at 8:27 AM, baktra said:

you should know that the _graphics() function returns the actual IOCB number used to open the S: device.

It is not guaranteed to be IOCB #6 (like in Atari BASIC)

 

 

I see the reason in your example, I ended up storing the IOCB in a location, there is a routine for getting the iocb from descriptor:

 

;setscreen fd - file descriptor for screen
.proc __setscreen
    jsr fdtoiocb
    sta SIOCB
    rts
.endproc
SIOCB: .byte $00

that means either to drag it as parameter or call as a set method:
 

 int fd = _graphics(8);
_setscreen(fd);

I wonder if this is needed at all or cc65 can just guarantee channel 6

[sanny]

cc65 uses the first free IOCB.