[Coco] ccasm question

[Hugo Dufort]

Re-reading the previous message and checking the code I've pasted, I 
need to add a few explanations.
- There was a typo in "hhcolors", it should have been "hcolors", e.g. 
the name of the globally-defined variable.
- I have added that last line ("sta hcolors") as an example of a 
reference to a global variable.
- That last line was not part of the original procedure, and it gives a 
"Symbol Doesn't Exist" error when compiling.

Sorry for the conflicting statements in my previous messages!

I can paste the whole code for my HSCREEN procedure here, but it's very 
long and It's by no means optimized. I would like this procedure to set 
global variables when it initializes the graphics port, so that other 
procedures and code sections will have the chance to use these values to 
make their work easier. For example, I would like to set a variable 
defining the number of pixels per byte in the current graphics mode. If 
I can't refer to global variables, then I will map these values to 
specific (fixed) memory locations, but I prefer writing "cleaner" code.

I'm not (yet) proficient in 6809 ASM, so I'm not using all the nice 
tricks, optimizations and addressing modes available.

Here is my "horrible" ASM code for HSCREEN:

=======

* procedure HSCREEN
hscreen    proc    width:word,height:byte,colors:byte
     begin    hscreen
* video mode 0xff98
     ldx    #$ff98
     lda    ,x
     ora    #%10000000
     sta    $ff98    video mode

* Video Resolution (FF99):
     ldb    #0    used to sum up bits
testw    ldx    width,u
     lda    colors,u
     leax    a,x    width+colors = vidmode unique code
testw644@    cmpx    #644    test width+colors
     bne    testw642@
     orb    #%11101
     bra    testh@
testw642@    cmpx    #642
     bne    testw516@
     orb    #%10100
     bra    testh@
testw516@    cmpx    #516
     bne    testw514@
     orb    #%11001
     bra    testh@
testw514@    cmpx    #514
     bne    testw336@
     orb    #%10000
     bra    testh@
testw336@    cmpx    #336
     bne    testw324@
     orb    #%11110
     bra    testh@
testw324@    cmpx    #324
     bne    testw322@
     orb    #%10101
     bra    testh@
testw322@    cmpx    #322
     bne    testw272@
     orb    #%01100
     bra    testh@
testw272@    cmpx    #272
     bne    testw260@
     orb    #%11010
     bra    testh@
testw260@    cmpx    #260
     bne    testw258@
     orb    #%10001
     bra    testh@
testw258@    cmpx    #258
     bne    testw176@
     orb    #%01000
     bra    testh@
testw176@    cmpx    #176
     bne    testh@
     orb    #%10110
     bra    testh@
     * let's decode the vertical resolution (h)
testh@    lda    height,u
testh192@    cmpa    #192
     bne    testh200@
     orb    #%00000000
     bra    setmode@
testh200@    cmpa    #200
     bne    testh225@
     orb    #%00100000
     bra    setmode@
testh225@    cmpa    #225
     bne    setmode@
     orb    #%01100000
setmode@    stb    $ff99    set video resolution using built mask

     *vscroll register bits{0-4} - set to 0
     lda    #0
     sta    $ff9c

     * init vertical offset at $60000 (D << 10 + E << 3) 
addr=11000000:00000000:000, D=0110 0000, E=0000 0000
     lda    #192
     sta    $ff9d    vertical offset1, bits 11-18
     lda    #0
     sta    $ff9e    vertical offset2, bits 3-10

     * init graphics and enable Coco3 mode
     lda    $ff90    init0 - load mask from memory
     anda    #%01111111    kills bit7 (Coco12/3 mode)
     ora    #%01000000    sets bit6 (MMU enable)
     sta    $ff90
     endproc

========

Le 2015-03-10 10:29, Robert Gault a écrit :
> Hugo Dufort wrote:
>> I am using the defined variables suchas as "hwidth" to store global 
>> values,
>> they're not pointers or anything else.
>>
>> I have not sent the whole HSCREEN procedure, because it is 4 pages 
>> long and what
>> it does is not relevant to the question I've asked.
>>
>> There are no typos in the code. It compiles and it works just fine. 
>> Right now I
>> can use my program to open any hi-res screen resolution (for example, 
>> 256x225 in
>> 16 colors), draw rectangles and set pixels.
>>
>> My question only relates to acessing global variables defined here, 
>> such as
>> "hwidth" or "hheight"
>>
>> Hugo
>>
>
> Hugo,
>
> Read my previous message carefully. How do you account for variables 
> used in the procedure that were not defined in your message?
>
> Robert
>
>
>
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