Translate the following MIPS instructions into 32 bit instructions

Question

I'm trying to translate the following MIPS instructions into 32 bit machine code (using Big-endian):

swc1 $f1 8($t0)

What I did was:

111001 00001 01000 00001000

I'm only sure about the translation of swc1, but not the others. I've googled a lot but couldn't find the number of $f1. I also read this thread: Link to a similar question However I'm still not sure if I should use 00001 for $f1. As for the machine code of offset 8 and $t0, am I doing it right?

Answer 1

Since instructions are 32 bit, the machine code format has space for a 16 bit immediate, as follows:

111001 Rs[5] Ft[5] Offs[16]

(The numbers in brackets indicate bit counts.)

Note that $t0 is register #8, and $f1 is indeed register #1. As such your instruction is:

111001 01000 00001 0000000000001000
= 1110 0101 0000 0001 0000 0000 0000 1000 = E5 01 00 08

You can of course verify it using a trusted assembler:

1 0000 E5010008      swc1 $f1, 8($t0)