Compatibility With The Tms320C1X/C2X/C2Xx/C5X Assembler Directives - Texas Instruments TMS320C54x User Manual

4.2 Compatibility With the TMS320C1x/C2x/C2xx/C5x Assembler Directives

Compatibility With the TMS320C1x/C2x/C2xx/C5x Assembler Directives
This section explains how the TMS320C54x assembler directives differ from
the TMS320C1x/C2x/C2xx/C5x assembler directives.
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The 'C54x .long and .float directives place the most significant word of the
value at the lower address, while the 'C1x/C2x/C2xx/C5x assembler direc-
tives place the least significant word at the lower address. Also, the 'C54x
.long and .float directives automatically align the SPC on an even word
boundary, while the 'C1x/C2x/C2xx/C5x assembler directives do not.
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Without arguments, the 'C54x and the 'C1x/C2x/C2xx/C5x assemblers
both align the SPC at the next 128-word boundary. However, the 'C54x
.align directive also accepts a constant argument, which must be a power
of 2, and this argument causes alignment of the SPC on that word bound-
ary. The .align directive for the 'C1x/C2x/C2xx/C5x assembler does not
accept this constant argument.
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The .field directive for the 'C54x packs fields into words starting at the most
significant bit of the word. The 'C1x/C2x/C2xx/C5x assembler .field direc-
tive places fields into words starting at the least significant bit of the word.
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The .field directive for the 'C54x handles values of 1 to 32 bits, contrasted
with the 'C1x/C2x/C2xx/C5x assembler which handles values of 1 to 16
bits. With the 'C54x assembler, objects that are 16 bits or larger start on
a word boundary and are placed with the most significant bits at the lower
address.
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The 'C54x .bss and .usect directives have an additional flag called the
alignment flag which specifies alignment on an even word boundary. The
'C1x/C2x/C2xx/C5x .bss and .usect directives do not use this flag.
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The .string directive for the 'C54x initializes one character per word, unlike
the 'C1x/C2x/C2xx/C5x assembler .string, which packs two characters
per word. The new .pstring directive packs two characters per word, as the
former .string did.
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The following directives are new with the 'C54x assembler and are not
supported by the 'C1x/C2x/C2xx/C5x assembler:
Directive Usage
.xfloat Same as .float without automatic alignment
.xlong Same as .long without automatic alignment
.pstring Same as .string, but packs two chars/word
Assembler Directives 4-7