The Nios® V/m processor is based on the RV32IA specification, and there are 6 types of instruction formats. They are R-type, I-type, S-type, B-type, U-type, and J-type.
Table 36. Instruction Formats (R-type)
Bit Field (R-type) |
31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
funct7 |
rs2 |
rs1 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
rs1 |
funct3 |
rd |
opcode |
Table 37. Instruction Formats (I-type)
Bit Field (I-type) |
31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
imm[11:0] |
rs1 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
rs1 |
funct3 |
rd |
opcode |
Table 38. Instruction Formats (S-type)
Bit Field (S-type) |
31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
imm[11:5] |
rs2 |
rs1 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
rs1 |
funct3 |
imm[4:0] |
opcode |
Table 39. Instruction Formats (B-type)
Bit Field (B-type) |
31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
imm[12] |
imm[10:5] |
rs2 |
rs1 |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
rs1 |
funct3 |
imm[4:1] |
imm[11] |
opcode |
Table 40. Instruction Formats (U-type)
Bit Field (U-type) |
31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
imm[31:16] |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
imm[15:12] |
rd |
opcode |
Table 41. Instruction Formats (J-type)
Bit Field (J-type) |
31 |
30 |
29 |
28 |
27 |
26 |
25 |
24 |
23 |
22 |
21 |
20 |
19 |
18 |
17 |
16 |
imm[20] |
imm[10:1] |
imm[11] |
imm[19:16] |
15 |
14 |
13 |
12 |
11 |
10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
imm[15:12] |
rd |
opcode |