NIOS II Custom Instruction blocks printf

Altera_Forum · ‎11-13-2009

Hi

I am trying to add custom Instruction block to my SOPC Builder Design but i find the printf gets blocked whenever i add custom instruction to my design .I even powered off and powered on by board but still i see that the Printf doesnt print on the console

Custom Instruction is just a combinatorial adder

I am able to see in the registers the addition happening well but the result i am unable to print it on to screen

Please help me out

regards

M Kalyansrinivas

Altera_Forum · ‎11-13-2009

I´m not shure but the first think which comes into my mind was maybe there is something wrong with your Avalon interface in your custom block. So it would help if you can post your HDL Code and the c-File so that we can see how you want to use it.

Altera_Forum · ‎11-21-2009

I´m afraid you forgot to implement the Avalon interface and it´s combinational logig. At least the entity looks somehing like that

module xyz(CLK, RST, READDATA, WRITEDATA, READ, WRITE, ADRESS);
input CLK;
input RST;
input  READDATA;
input READ;
output  WRITEDATA;
input WRITE;
input  ADRESS;

At SOPC Builder you conect these signals as Avalon slave to the signals. I think they have the same name or sounds simular.

You also need some logig to put data on the Avalon inteface if you want to read it from your c-code.


always@ (posedge CLK)
beginif(WRITE == 1'b1)
begincase(ADRESS)
begin
...
end
end
else
begin
if(READ == 1'b1)
begincase(ADRESS)
beginresult_adress: READDATA <= result;
end
end
end
end

In your c-Code you can then write:


result = IORD_32DIRECT(XYZ_BASE,result_adress);

I´m not sure if that´s all. I´m afraid there is something missing but I think the basics get clear. And I hope it is that what you like to do ;).

Altera_Forum · ‎11-23-2009

Hi mki

Thank you for the reply but i cannot connect the combinatorial logic of dataa and datab to avalon slave as i am trying to make it as a custom instruction

Custom Instruction will directly connect with the alu instead of being as slave for avalon bridge So i think in custom instruction i should not connect to avalon slave rather i should do it as a nios_custom_instruction_slave

Thank you

M Kalyansrinivas