Can't functions call other functions?

SystemVerilog
, ,
1

I’m getting the error “functions can’t enable tasks”. Why am I getting this error when I’m not using tasks (as far as I know) ?

I’m trying to improve the readability of my code by splitting it up into functions - and I will want to add other code in the always_ff block.

The compiler doesn’t like this:

function void HandleRxIdle;
endfunction

function void HandleReceiveStates;
  unique case( rxState )
    RX_IDLE         : HandleRxIdle();
  endcase
endfunction

always_ff @( posedge clk )
begin
  HandleReceiveStates();
end

But it doesn’t complain if I do this:

function void HandleRxIdle;
endfunction

always_ff @( posedge clk )
begin
  unique case( rxState )
    RX_IDLE         : HandleRxIdle();
  endcase
end

What is the problem here?

2

What happens if you change

HandleReceiveStates;

to

HandleReceiveStates();

?

3

In reply to sbellock:

Same thing I’m afraid. I even tried putting empty brackets on the function definition itself but that made no difference either.

function void Oranges();
endfunction

function void Apples();
  Oranges();
endfunction

Same deal above. I added these to remove any dependency on my always_ff() block.

4

In reply to SparkyNZ:
It would help if you learn how to post a minimal reproducible example. Maybe the problem is somewhere else. This code below ran on 4 different tools:

module top;
  bit clk,rxState;
  localparam RX_IDLE = 0;
  
  function void HandleRxIdle;
endfunction
 
function void HandleReceiveStates;
  unique case( rxState )
    RX_IDLE         : HandleRxIdle();
  endcase
endfunction
 
always_ff @( posedge clk )
begin
  HandleReceiveStates();
end
  
initial begin
  #5 clk =1;
  #5 $finish;
end
endmodule
5

In reply to dave_59:

In reply to SparkyNZ:
It would help if you learn how to post a minimal reproducible example. Maybe the problem is somewhere else. This code below ran on 4 different tools:

Apologies for not providing a complete module file. If your example module works on 4 different tools then I guess it is a problem/feature specific to Quartus II.

As you can see below, we get the same problem:

710×517 36 KB

6

In reply to SparkyNZ:

Yes, this is a tool bug. I’m guessing it doesn’t like functions calling void functions.