Basic Machine Level Word Alignment Question

Hi Randy,

I believe you are correct. Can you point to the page/section you need more explanations about?

Please see page 71 (3.7.5) of the document:

http://www-s.ti.com/sc/techlit/SPRU732

"The C64x/C64x+ DSP can access words and doublewords at any byte boundary using nonaligned loads and stores. As a result, word and doubleword data

does not need alignment to 32-bit or 64-bit boundaries. No other memory access may be used in parallel with a nonaligned memory access."

So it needs to be 16-bit aligned indeed.

Hi Mariana,

Thank you for your prompt and thoughtful answer. However, I think we have miscommunicated. Based on your response, I would have expected you to say "I believe you are incorrect."

By "word" I meant 32-bit data value, e.g., a uint32_t in C99's stdint.h syntax.

It does indeed seem to indicate you can perform non-aligned load/stores, and that to the byte level, but that seems to be contradicted by the main store instruction, STW, as described on p. 462 of the same document you referenced. Note the last sentence on that page states:

  "Word addresses must be aligned on word (two LSBs are 0) boundaries."

So that would seem to indicate you cannot store to non-aligned boundaries.

For example, can I store the value 0xfedc 4321 to address 0x0000 0003, so that in memory we would have

Addr.            Data

00000003  21

00000004  43

00000005  dc

00000006 fe

--Randy

Ah! Thanks Mariana!

--Randy