I-Type instruction use a 12-bit immediate value extended to 32-bit by sign extension.
[I-Tpye]
+-------------------------------------------------------------------------------------------------+
| 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 |
+------------------------------------+--------------+--------+--------------+---------------------+
| imm_i | rs1 | funct3 | rd | opcode |
+------------------------------------+--------------+--------+--------------+---------------------+
Load data from memory to Rd.
lw rd, offset(rs1)ALU(algorithmic logic unit) is used to calculate the memory address.
Base address is rs1 and offset is sign extended imm_i.