Compiler/MSP430F5529: I couldn't find a htobe32() function...

Stuart MacDonald

Part Number: MSP430F5529

Tool/software: TI C/C++ Compiler

...or similar function, so I wrote my own.

Does it actually exist and I just missed finding it?

It's my first crack at MSP430 asm. I'm sure there are things I'm not doing correctly, but I don't know what I don't know. Any suggestions for improving the code?

...Stu

/*
 * Assembly level utilities
 *
 */

extern unsigned long __swap_long(unsigned long x);

;
; Assembly level utilities
;

        .global __swap_long

__swap_long:
        swpb    r12
        swpb    r13
        xor.w   r12,r13
        xor.w   r13,r12
        xor.w   r12,r13
        reta

over 9 years ago

0 George Mock over 9 years ago

TI__Guru**** 253380 points

I haven't had a chance to try it yet. But it passes basic inspection. I don't see any problems.

Thanks and regards,

-George

0 George Mock over 9 years ago in reply to George Mock

TI__Guru**** 253380 points

One additional thing ... For 16-bit values, there is an intrinsic named __swap_bytes. Read more about it in the MSP430 compiler manual.

Thanks and regards,

-George

0 Stuart MacDonald over 9 years ago in reply to George Mock

Prodigy 120 points

Hi George,

I am aware of __swap_bytes() (which outputs SWPB :-))

Thanks for the code review. It seems so simple that it must be problematic, so I'm nervous. It works though.

...Stu

0 David Schultz over 9 years ago

Guru 26085 points

mspgcc included this function in endian.h but when TI took over the MSP430 GCC compiler they didn't include this header. It used functions described in <bits/byteswap.h> which also didn't survive the transition. The code used in mspgcc was:

        .section .text
        .global __bswap_32
__bswap_32:
        swpb    r14
        swpb    r15
        mov.w   r15, r13
        mov.w   r14, r15
        mov.w   r13, r14
        XRET

0 Stuart MacDonald over 9 years ago in reply to David Schultz

Prodigy 120 points

Thanks!

I checked the cycle lengths, mov and xor are the same, so my version is equivalent. Always nice to have confirmation.

...Stu

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Compiler/MSP430F5529: I couldn't find a htobe32() function...