Use of a bit from a packed array as a ref to task

SystemVerilog
,
1

Hello,
I have a task that receives a logic as a ref, e.g. :
task MyTask(ref logic ref_input)
I send this task signals from an interface. If the signal is a single bit it works OK, but I cannot use a one bit slice from a packed array as input. i.e. :
interface myInterface
logic myBit;
logic [7:0] myByte;
…

MyTask(myBit); //works OK
MyTask(MyByte[0]); //causes elaboration error vsim-8465
MyTask(MyByte[0:0]); //also causes elaboration error vsim-8465

My Question is :
How to convert the input MyByte[0] to appropriate expression(without defining another signal and assigning myByte[0] to it) ?
Thanks

2

In reply to shaygueta:

SystemVerilog does not allow a select of a packed array to be passed by reference. Do you really need pass by reference, or will input or output work for you?

3

Hi,
Yes, I need to pass it by ref, because the task waits for the signal to change value

4

In reply to shaygueta:

Can you pass then entire byte by ref to the task, then select the bit inside the task? You can add an extra argument that indicates which bit to select.

5

In reply to dave_59:

Hi,
No,because what I want is a general task. Sometimes the signal I will send is a single bit, and in other cases it will be a single bit from an array(that can be either packed or unpacked).In such a case, I cannot assume I know the size of the array in advance.
i.e. I might need :
logic myBit;
logic [7:0] myByte;
logic [31:0] myWord;
…

MyTask(myBit,0); //Argument is the signal
MyTask(MyByte,6); //Argument is bit #6 of the signal
MyTask(MyWord,18); //Argument is bit #18 of the signal

in such a case, what will be the task definition?

6

In reply to shaygueta:

It would help to have a lot more details about what you are trying to accomplish, otherwise we are going to keep iterating.

You can place your task inside a parametrized class

class MyClass #(int size);
static MyTask(ref logic [size-1:0] signal, int position);
...
endtask

MyClass#($bits(MyBit))::Mytask(MyBit,0);
MyClass#($bits(MyByte))::Mytask(MyByte,6);
MyClass#($bits(MyWord))::Mytask(MyWord,18);

If you only need to be informed about a changing bit, you can create an event, and pass that event to the task

task Mytask(event expr);
  ...
  @expr ...
endtask

fork
  event e;
  @mybit ->e;
  Mytask(e);
join_none
fork
  event e;
  @myByte[6] ->e;
  Mytask(e);
join_none
7

In reply to shaygueta:

I think you can pass the bit in packet array to a logic type variable first, sort of

logic a;
a = packet_array[0];
#you can also change the data type before you call the task
task MyTask(ref logic a)