From: Andrew Crabtree <andrewc AT typhoon DOT rose DOT hp DOT com>
Message-Id: <199707222205.AA051199111@typhoon.rose.hp.com>
Subject: Re: How to outw ?
To: tcho AT polbox DOT com
Date: Tue, 22 Jul 1997 15:05:11 PDT
Cc: djgpp AT delorie DOT com
In-Reply-To: <33D519FB.499A@polbox.com>; from "Tomasz Chojnacki" at Jul 22, 97 10:37 pm
Precedence: bulk

> I have the following problem:
> Why can't I compile the below code:
Like the error message says, its not a valid opcode. 

>     outw %ax, $0x2100
> E:/DJGPP/TMP\cca00041:13: Error: operands given don't match any known

From Intels Pentium Processor Users Manual Volume 3

Out - Output to Port

OUT imm8,AL
OUT imm8,AX
OUT imm8,EAX
OUT DX,AL
OUT DX,AX
OUT DX,EAX

The problem is the immediate field is only 8 bits.  You need to move the 
value for the port into DX and then use it instead.  Remember to 
switch opcode order for AT&T syntax.

>     outw %ax, $0x21
Here 0x21 will fit in an 8 bit value no problem, 0x2100 above is too big.


--
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