assembler syntax

[MFlamer]

Why are there 2 types of syntax? I see reference to an "Architectural" syntax in the Assembly Programming Manual but it's not clear what the difference is between them. If I try.....

Code: Select all

 ldw 	r1, cp[r10]

I get the following error,

../src/test.S:29: Error: A00049 no format matching for instruction: 'ldw'

if I try:

Code: Select all

LDW 	r1, cp, r10 

I get the following error,

../src/test.S:31: Error: A00000 Use of "LDW" outside of architectural syntax mode.

What's up?

[MFlamer]

OK, I see the XC-1 Architecture manual does list the registers allowed for use with each instruction...and cp is now valid in ldw.

[Bianco]

The architectural assembler maps 1 to 1 to the instruction set.
The other assembler is a bit less verbose and easier to use, it has assembler instructions that can map to different processor instructions, for example: a processor might have two jump instructions: one to jump forward and one to jump backward. With the easier assembler you only require 1 instruction and it will map to the right processor instruction depending on the label you jump to.

There are assembler directives to switch between the two assembler types.

[segher]

And your actual problem is there is no "ldw r1,cp[r10]"
instruction; you need to write something like

Code: Select all

ldaw r11,cp[0]
ldw r1,r11[r10]

HTH,

Segher

[MFlamer]

Got it.

Is there a way to set a register alias? something like

Code: Select all

.set A, r0

Thanks.

[richard]

Is there a way to set a register alias?

There's no mechanism built into the assembler itself. However assembly files with an uppercase .S extension are run through the C preprocessor, so you could use a preprocessor macro instead:

Code: Select all

#define A r0

[MFlamer]

I forgot about that! Cool, I can do this and more with the preprocessor. Thanks.

[MFlamer]

How are the following instructions any more useful then a simple add or sub? I must be missing something...