help me with opcodes please

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terex

Joined: 31 Dec 2003
Posts: 16
Location: Saint-Petersburg, Russia

terex 05 Jan 2004, 03:20

I'm newbie in this topic. Is this right?

Code:

      ;1)
     ;mov    ebx, scan2ascii {
                      db 0xC7
                     db 0xC3
     ps2a rd 1
   ; }

        ;2)
     ;mov    ebx, [screenpos] {
                     db 0xC7
                     db 0x1D
     ppsp1 rd 1
  ; }

        ;3)
     ;add    [screenpos], 0x2 {
                     db 0x81
                     db 0x5
      ppsp2 rd 1
  ; }

        ;4)
     ;mov    [screenpos], ebx {
                     db 0x89
                     db 0x1D
     ppsp3 rd 1
  ; }

ps2a contains offset of scan2ascii label, ppsp[n] contains offset of screenpos one. You may ask me, why do i need code like this. Answer is simple: that piece of code will execute in pagintation pmode, so i don't know real addresses of labels in compile-time.

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sorry for my english

05 Jan 2004, 03:20

JohnFound

Joined: 16 Jun 2003
Posts: 3499
Location: Bulgaria

JohnFound 05 Jan 2004, 06:02

Why not:

Code:

ps2a:   mov   ebx, [0]
ppsp1: mov   ebx, [0]
ppsp2: add   [0], 0x2
ppsp3: mov   [0], ebx

and then you can use: [ps2a+2], [ppsp1+1], etc. to fill real addresses.

or better use on runtime:

Code:


; compute the address in esi. 

   mov   ebx, [esi]
   mov   ebx, [esi]
   add   [esi], 0x2
   mov   [esi], ebx

05 Jan 2004, 06:02

terex

Joined: 31 Dec 2003
Posts: 16
Location: Saint-Petersburg, Russia

terex 05 Jan 2004, 08:07

Oh, chets, it is really mutch more better! Thanks. Why i didn't get this solve myself? Sad

Btw, i compiled instruction... and sow that my interpretatioon of opcode-building is not very right Smile

Opcodes for all of written commands are wrong Confused

_________________
sorry for my english

05 Jan 2004, 08:07

JohnFound

Joined: 16 Jun 2003
Posts: 3499
Location: Bulgaria

JohnFound 05 Jan 2004, 08:37

terex wrote:

Opcodes for all of written commands are wrong

Well, I never check them. Smile

To programm in hex, you need hex editor, not an assembler. Wink

I can't remember who was, but someone wrote: "Real man code in hex." Very Happy

Regards

05 Jan 2004, 08:37

scientica
Retired moderator

Joined: 16 Jun 2003
Posts: 689
Location: Linköping, Sweden

scientica 05 Jan 2004, 11:35

There are an opcode tutotial on the http://board.win32asmcommunty.net by the Svin (very good stuff IMO), if you want to do opciding there are a few macros for modrm,sib (and single byte instruction /reg), which accepts binary (eg bsib 01,100,001).

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- Bradley Kuhn

05 Jan 2004, 11:35

terex

Joined: 31 Dec 2003
Posts: 16
Location: Saint-Petersburg, Russia

terex 05 Jan 2004, 21:41

Quote:

someone wrote: "Real man code in hex."

My friend told me that one ultraexpirenced professor in his university have said it to students during first lesson of programming Wink

2scientica: i have read good (imho) opcode tutorial in my native language on wasm.ru... and it didn't help me Smile

It's not important. Because i'm not going to opcoding. I just want to be able use it when it really need. But thanks in any case.
About macroses. Continueing this idea we can got a set of macroses which translate mnemonic instructions to the opcode Smile

But we allready have so many different assembler compilers Laughing

_________________
sorry for my english

05 Jan 2004, 21:41

Madis731

Joined: 25 Sep 2003
Posts: 2139
Location: Estonia

Madis731 05 Jan 2004, 23:25

I guess I must be a "real man" Laughing

I have a PC-E500 pocket computer from Sharp and I could code only in BASIC in it until I found out that I can call memory addresses from BASIC Very Happy

Now I poke to some memory addresses, call it and later peek the values that should have changed by running my code:)
Fun, ain't it?
It has only 26K of RAM, so I can't do any large programs in it:(
...but I'm building a dungeon game (or was it MUD game) I guess it will be about 2KB

P.S. I'm a really lucky man, 'cause the computer allows me to code in hex AND in dec too Cool

05 Jan 2004, 23:25

JohnFound

Joined: 16 Jun 2003
Posts: 3499
Location: Bulgaria

JohnFound 05 Jan 2004, 23:46

Madis731 wrote:

I guess I must be a "real man"
I have a PC-E500 pocket computer from Sharp and I could code only in BASIC in it until I found out that I can call memory addresses from BASIC

Well this is classics. Smile

Now you should write not a game, but simple assembler, to make you live easyer. Then write a game - it will be faster.

Or better write some Win32 programm with FASM. Very Happy

Regards.

05 Jan 2004, 23:46

Madis731

Joined: 25 Sep 2003
Posts: 2139
Location: Estonia

Madis731 07 Jan 2004, 00:18

...some work has been done for me by some fine chinese and japanise people, but I don't understand their language so I'm just testing the assemblers how would they work. And of course, I don't have any cable between my PC and PC(PocketComputer), so every byte must be hand-written to the PC-E500 Evil or Very Mad

But I can manage, I'll keep my code size optimized & everyone will be happy Wink

But thanks for the advice, I'll do that some day inside my PC(pocket). As you said, my life would be MUCH easier Razz

07 Jan 2004, 00:18

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