How to pass an address to ASM function?

[wallaby]

This is basic ASM question. What I'm trying to do is use assembly (instead of a macro) to change the player sprites and colors to anything.

 

 

change_player_color
  STA player0color
  STY player0color+1
  LDA #16
  STA player0height
  RETURN

 

If I call the function this way: temp1 = change_player_color(flash_lo, flash_hi)

 

This changes the color, but not the right way. It looks like it's just getting random data and all the lines are different colors.

 

I'd like to simplify this so I only need to pass the label of the data object. Like:

 

temp1 = change_player_color(flash_color)

 

Another thing, is how can I manipulate something already in a register? Can I use other registers in an expression? LDA x + y? Can I manipulate the current register on the same line? LDA a + 1?

 

I have this working with macros, but do macros duplicate your code for every permutation?

[wallaby]

Hmm. Maybe macros don't behave like I thought they did. I thought they sort of allowed you to programmatically duplicate code. But when I call the same macro twice, it looks like it acts more like a function. In that case, it shouldn't duplicate and using a macro is easier. Unless my interpretation is wrong.

[bogax]

This is basic ASM question. What I'm trying to do is use assembly (instead of a macro) to change the player sprites and colors to anything.

change_player_color
  STA player0color
  STY player0color+1
  LDA #16
  STA player0height
  RETURN

If I call the function this way: temp1 = change_player_color(flash_lo, flash_hi)

 

This changes the color, but not the right way. It looks like it's just getting random data and all the lines are different colors.

 

I'd like to simplify this so I only need to pass the label of the data object. Like:

 

temp1 = change_player_color(flash_color)

 

Another thing, is how can I manipulate something already in a register? Can I use other registers in an expression? LDA x + y? Can I manipulate the current register on the same line? LDA a + 1?

 

I have this working with macros, but do macros duplicate your code for every permutation?

 

macros do duplicate code

they're kinda like inlined functions

"temp =" is bB and there's not much facility built into bB for getting stuff from asm to bB

(you just do it in asm)

a bB function can supply a value for an assignment but it has a bunch of overhead you probably don't need

for one thing it's a subroutine for another it always (in effect) passes at least two parameters whether you

want them or not

 

if your player data object is in RAM and therefore uses 1 byte addresses then you're asm might be something like this

 

 

   macro {1}
   asm
   lda {1}
   sta player0color
   lda #16
   sta player0height
end
end

 

you'd pass the macro a number which is the address of the color data (a single byte)

in bB that would be either a numeric constant or a variable name

the variable name is an alias for the number which is the address of a location in memory

it gets interpreted as an address in the asm because I didn't tell it otherwise

 

if you passed "a" as a parameter that would be equivalent to

 

lda $d6

 

$d6 is the location of variable a

 

if the asm were

 

lda {1}+1

 

that would be address $d7 dasm would do the math it's a constant expression and that would be variable b (they're in order in memory)

 

if the asm were

 

lda #{1}

 

and you passed (variable name) "a" as a parameter then player0color would get set to $d6

 

the bB equvalent of that (my) macro would be

 

 

   macro
   player0color = {1}
   playerheight = 16
end

 

 

I don't think that helps you much though (I don't think any of that is what you want)

 

could you give a little more information (maybe a little more explicit)

[wallaby]

What I'm trying to come up with is an efficient way to change player sprites and colors in bB.

 

I didn't want to use a macro because of the duplication of code. The overhead of a function isn't too much of a problem since I won't call it every frame, only occasionally.

 

I understand the assembly to set a sprite color or pixel data in DPC+. The problem is I don't know how to pass my address as an argument to the function. Or how to pass a label as an argument. (Since they're 16-bit.)

[wallaby]

 

 

could you give a little more information (maybe a little more explicit)

 

Here is my macro currently. This works. But does it duplicate the code for every label I pass to it? If I pass "monster" or "monster2" or "monster3" is this code getting duplicated for each one?

 

 

 macro _change_sprite_color_player0 ;1 datalabel (myskele)
  asm
  LDX #<{1}
  STX player0color
  LDA #((>{1}) & $0f) | (((>{1}) / 2) & $70)
  STA player0color+1
end
end

[bogax]

I don't see anything there that needs asm

you can't stx in bB but you don't need to

 

what is the nature of the label/parameter?

[wallaby]

 

 

what is the nature of the label/parameter?

 

It's either a list of colors or sprite data. (Using DPC+ kernel)

 

Imagine a situation where you want to re-use sprite data. If you use bB, you might set player0 to a sprite using the syntax "player0: %000000, etc"

 

What if you want to then use that same sprite for player1? If you use the same syntax "player1: %00000, etc" you just duplicated the data. The more sprites you want to use, more this situation spirals out of control.

 

So, you can set the sprite using the data format. Then you can reference that data for your players and it's only defined once.

 

 

data skele
 %00111000
 %01111100
 %01111100
 %01111100
 %01101000
 %01101000
 %00010100
 %00010100
 %01111110
 %01111110
 %10111101
 %10111101
 %00111000
 %00111000
 %01000100
 %01000100
end

 

I don't know of any way to set this data to a player object in bB.

 

player0: skele?

player1: skele?

 

But I know how it is set in ASM by examining the file generated by bB. So I have to either bypass bB using inline ASM or extend bB to use some new syntax. Modifying bB is much, much harder because the application is larger and I don't have a development environment set up for C.

 

That leaves one option - inline asm.

[bogax]

you can do that without asm

 

as far as I know there are only two uses of labels in bB

either as targets for goto's and such or as the name of a table in a data statement

 

if it's a goto target bB appends a "."

 

to get access in bB define constants for the labels

  data table
  xx, xx, etc
end
 
 const tablelo = <table
 const tablehi = >table
 
  ;the label
target
 
 const targetlo = <.target
 const targethi = >.target
[

I haven't got time to search now

 

but if you can find some of my previous posts there should be examples (somewhere )

 

 

edit: I found some old files and attached them here

because I thought they were probably from the (no longer working) link there

maybe a mistake because they appear to come from here

Edited September 15, 2016 by bogax