Custom Istruction

[Altera_Forum]

What is a Custom instruction ? Im doing a project where I have a verilog module that reads data from the audio codec and when the audio buffer gets full, I intend to read the buffer using a Nios processor and do some calculations. I first wanted to use IOR instructions to read the buffer. but then I heard about custom instructions. Can anyone help me exactly what it is?

[Altera_Forum]

It's a method of extending the ALU of the CPU. So you can map up to 256 'new' instructions to the ALU using custom instructions. It's good for short and simple operators like MAC (multiply and accumulate) for example. If you plan on sending a large buffer through some hardware acceleration normally a DMA and a dedicated hardware accelerator is usually the better approach. To learn more check out the custom instruction information on this page: http://www.altera.com/literature/lit-nio2.jsp

[Altera_Forum]

Thnx so much!