PUSH -> "clear" code doesn't work

flat assembler
Message board for the users of flat assembler.

Index > DOS > PUSH -> "clear" code doesn't work

Author

Thread

dieboy

Joined: 30 Dec 2004
Posts: 41
Location: Poland, Elblag

dieboy 18 May 2005, 18:37

Hello!

Code:

push ax
;is like :
sub sp, 2
mov ss:[sp], ax
;but in TASM

and how to write this code in FASM? if I write ... [ss:sp] i have an error. Can you tell me ?

_________________
...

18 May 2005, 18:37

YONG

Joined: 16 Mar 2005
Posts: 7997
Location: 22° 15' N | 114° 10' E

YONG 18 May 2005, 19:45

Try this:

Code:

                sub     sp, 2
                mov     bp, sp
                mov     [bp], ax

Your error was not related to ss. It was about [sp] which is illegal.

Listed below are the legal 16-bit Memory Addressing Modes:
- Displacement
- bx or bp
- si or di
- Any combinations of the above three

YONG

18 May 2005, 19:45

mike.dld

Joined: 03 Oct 2003
Posts: 235
Location: Belarus, Minsk

mike.dld 18 May 2005, 19:53

In 16-bit code there is no SP-relative addressing (only BP,BX,SI,DI can be used). But you can probably write

Code:

sub sp, 2
mov [esp], ax

_________________
http://ostin.googlecode.com/

18 May 2005, 19:53

YONG

Joined: 16 Mar 2005
Posts: 7997
Location: 22° 15' N | 114° 10' E

YONG 18 May 2005, 20:21

One more point.

Even though the [bp] addressing mode uses ss by default,
you may code [ss:bp] to make it clear and unambiguous.

YONG

18 May 2005, 20:21

MazeGen

Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia

MazeGen 18 May 2005, 20:59

mike.dld wrote:

In 16-bit code there is no SP-relative addressing (only BP,BX,SI,DI can be used). But you can probably write
Code:
sub sp, 2
mov [esp], ax     

You can never be sure that high word of ESP is zero, so MOVZX ESP,SP should be used before such code.

_________________
x86asm.net

18 May 2005, 20:59

dieboy

Joined: 30 Dec 2004
Posts: 41
Location: Poland, Elblag

dieboy 19 May 2005, 06:15

Ok. Thank you very much! Smile

_________________
...

19 May 2005, 06:15

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum