srli shifts bits to the right by a fixed amount, filling the vacated top positions with 0s. It is the constant-amount version of srl (which covers the mechanics and the all-important zero-fill detail); the i means immediate, a constant written into the instruction instead of taken from a register.

The form is srli rd, rs1, amount, with amount a fixed number from 0 to 31. Since a right shift halves a number for each place moved and the zero-fill treats the value as never-negative, srli is exact division of an unsigned number by a power of two: srli t0, t0, 1 halves t0, srli t0, t0, 2 quarters it.

Paired with a masking AND, it is the standard recipe for reading one field out of a packed value: shift the field you want down to the bottom, then andi to keep just its bits. To read the second byte of a word, shift right by 8 to bring it down, then AND with 0xff to isolate it.

Remember the fork between the two right shifts: srli always fills with 0s, which is right for raw bit patterns and never-negative numbers but wrong for signed values that might be negative — there a 0 would overwrite the sign marker. Signed division by a power of two belongs to srai instead. Choosing between them is always a statement about how you mean to read the register's bits.