NIOS II Custom Instruction blocks printf

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.

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;

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

result = IORD_32DIRECT(XYZ_BASE,result_adress);

Hi mki