topic Re: syntax for IX1 addressing in CodeWarrior for MCU

syntax for IX1 addressing

csosza — Sat, 20 Jun 2009 20:50:34 GMT

What is the syntax (an example) for IX1 addressing mode?

I tried this

LDHX #$0
SUB $0,X

Which results

1381 33 000000 45 0000 LDHX #$0
1382 34 000003 F0 SUB $0,X

But this is wrong. Opcode should be E0.

Re: syntax for IX1 addressing

bigmac — Sun, 21 Jun 2009 22:33:11 GMT

Hello, and welcome to the forum.

When the offset value is zero, this represents the special case of IX addressing mode, which is more efficient than IX1 addressing mode. So this is what the assembler uses. It means that the code requires one less byte, and one less execution cycle.

Note that the instructions SUB 0,X and SUB ,X are alternative forms of the same instruction.

Is there any particular reason that you would wish to force the use of IX1 mode?

Regards,

Mac

Message Edited by bigmac on 2009-06-22 01:38 AM

Re: syntax for IX1 addressing

csosza — Mon, 22 Jun 2009 01:27:09 GMT

Hi,

It would be an example in my demonstration (this would be a theoretical example).

Can I use IX1 addressing in CodeWarrior? I have the latest version.

(or is there any like using DB directives..?)

Re: syntax for IX1 addressing

peg — Mon, 22 Jun 2009 07:58:39 GMT

Hi,

Its like Mac said. If you use an offset of zero the assembler will use the more efficient IX mode.

If you really want IX1 mode, or to demonstrate it then the offset would have to be non-zero.

Re: syntax for IX1 addressing

CompilerGuru — Thu, 29 Oct 2020 09:44:35 GMT

For completeness, the assembler has a syntax for specifing the size of the operand:

 3043   27   000004 F0                      SUB $0,X; 3044   28   000005 E0 00                   SUB <$0,X; 3045   29   000007 D0 0000                 SUB >$0,X;

Note that this works with the assembler, not with the HLI in the compiler.

Especially for educationaly purposes, I would recommend to use an offset which requires the addressing mode and not just 0.

Daniel

Re: syntax for IX1 addressing

csosza — Tue, 23 Jun 2009 06:37:25 GMT

Thanks, I will use a non-zero address.