documentation for sxtb instruction

Galen Seitz said:

Where can I find documentation for the sxtb instruction that is listed on page 164 of SPRU430E?

Hi Galen,

Seems you're the first one to notice the documentation is missing for this instruction.  It basically does what is mentioned in the index.   I have been trying to track down the original specification for the instruction without luck.  If you can tell me what information you need I'll try to fill in the gaps. 

Galen Seitz said:

Will we ever see another update to SPRU430?  I know I have submitted bugs against rev E.  I'm sure others must have done so as well.

I will check on this with our tech pubs group.

Thank you

Lori

Lori Heustess said:

Seems you're the first one to notice the documentation is missing for this instruction.  It basically does what is mentioned in the index.   I have been trying to track down the original specification for the instruction without luck.  If you can tell me what information you need I'll try to fill in the gaps. 

I may have found some documentation for SXTB.  SPRU220D documents SXTB for the TMS320C27x.  Note that I found SPRU220D on the Net.  It doesn't appear to be available from TI's web site.  (In many ways, the web site seems to deny the existence of the C27x)

Is the C27x documentation of SXTB valid for the C2000 devices?

Do you happen to know if the compiler ever uses this instruction?

thanks,

galen

Do you have any more information on SXTB?  I'd like to use it in some assembly code, so it would be useful to know whether the documentation I found is valid.

thanks,

galen

Sorry to dig out an old post, but (it is still unanswered)...
Yes, the information in SPRU220 about the SXTB instruction seems to be identical for the C2000 (missing in SPRU430E).

I made a test run for all possible values of "SXTB AX", and the result is that in AX the upper byte is sign-extended with the most significant bit of the lower byte. I guess status bits are handled acc. to C27x, too.

Attached is the test output for all possible values.

1234.sxtb_test.zip

Regards
Felix

Thanks for going to the trouble of doing this.  You've confirmed what I had assumed, that this is the same instruction as the C27x.  The question now is why TI hasn't updated SPRU430.  Another puzzle to me is why the C27x docs, such as SPRU220, don't appear on the TI web site.

galen