6.8. Custom Instructions
Nios® V/g and Nios® II/f processors support custom instruction.
| Feature | Nios® V/g Processor | Nios® II/f Processor |
|---|---|---|
| Supported custom instruction types |
|
|
| Combinational instructions | Implemented in two cycles. | Implemented in a single cycle. |
| Multicycle instructions | Supports variable length multicycle instructions. | Supports fixed length and variable length multicycle instructions. |
| Extended instructions | Apply the signal ctrl[31:0] to select the appropriate instruction. | Apply the signal n[7:0] to select the appropriate instruction. |
| Internal Register Files instructions | Not Supported | Supported |
| Manager Interface | Nios® V Processor Custom Instruction Manager | Nios® II Processor Custom Instruction Manager |
| Agent Interface | Nios® V Processor Custom Instruction Subordinate | Nios® II Processor Custom Instruction Subordinate |
| Signals and Interface |
|
|
| Built-in functions (To use non-integer types with instructions) | Not supported | Supported |
| FPH2 Hardware | Replaced with internal FPU | Supported |
3 alu_result is not equivalent to clk_en.
4 Nios® V Processor Custom Instruction does not support clk_en signal.