CODEWITHSUNDEEP
assembly
Peach IceTea
Peach IceTea

Reputation: 55

Assembly instruction confusion, rrux.w and rrum.w

I am currently reading some assembly instructions, and I see that two instructions, rrum.w and rrux.w, keep coming up. I googled these two and did not find anything on it. What do they and how are they are used?

Architecture: MSP430.

Upvotes: 0

Views: 332

Answers (1)

Martin Rosenau
Martin Rosenau

Reputation: 18503

The RRUM instruction can even be found on the Wikipedia entry for the TMS 430.

Using Google I found this document describing both instructions:

http://www.win.tue.nl/~johanl/educ/RTcourse/MSP430%20-%20general.pdf

rrum: Shift right logical register

rrux: Shift right logical memory location

If you are confused by the ".w": This is the instruction size. Some assemblers add ".w" for 32-bit operation and ".h" for 16-bit operation. Other assemblers use ".l" for 32-bit and ".w" for 16-bit so the meaning of ".w" differs from assembler to assembler. ".b" is used for 8-bit operation.

TMS 430 seems to use ".a" or ".b" only in conjunction with the rrum/rrux operations. However some assemblers may "unify" the meaning of the suffixes so ".w" is always used for 16-bit (or 32-bit?) operation instead of ".a".

Upvotes: 2

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