Hi SV forum
lets assume that I have the following task.
task run();
do_something;
endtask
task do_something();
forever begin
@ (posedge signal);
wait_some_time;
act;
end
endtask
when signal first rise task do_something starts.
How can I kill the current task thread if a new signal event occurs before the old one finished.
In reply to shimonc:
Here is a Sample Code which works ::
reg clk = 0 ;
initial begin
fork
begin
#2 clk = ~clk ; // 1st Posedge at #2
#2 clk = ~clk ; // Occurs at #4
#2 clk = ~clk ; // 2nd Posedge at #6
#2 clk = ~clk ; // Occurs at #8
#2 clk = ~clk ; // 3rd Posedge at #8
#2 clk = ~clk ; // Occurs at #10
end
join
$display("TIME:%0t All Clks Triggered",$time) ;
$finish();
end
initial begin // This is similar to task do_something()
process Sub ;
semaphore sema= new() ;
fork
begin
forever @ ( posedge clk )
begin
if( Sub != null )
begin
Sub.kill();
$display("TIME:%0t Child Killed ",$time);
end
sema.put(1);
end
end
begin
bit b ;
forever begin
fork
begin
Sub = process::self();
sema.get(1); // Will Unblock at #2 ; #6 ; #10
$display("TIME:%0t Child Starts ",$time);
// Below if-else block is to be replaced by :: wait_some_time ; act ;
if ( b == 0 ) // For 1st Iteration let the thread Complete before Next posedge of CLK
begin
b++ ;
#3; // Will Complete at 5 Time Unit so that it can wait for posedge at #6 !!
$display("TIME:%0t Child Completes ",$time);
end
else // For 2nd Iteration let the thread still be running so that we kill it at next edge of CLK
begin
#5; // Will Complete at 6 + 5 i.e 11 Time Unit so that it can be killed at posedge at #10 !!
end
end
join
end
end
join
end
It gives me Output ::
**TIME:2 Child Killed
TIME:2 Child Starts
TIME:5 Child Completes
TIME:6 Child Killed
TIME:6 Child Starts
TIME:10 Child Killed
TIME:10 Child Starts
TIME:12 All Clks Triggered**
In reply to shimonc:
If you just want to kill and restart, you can do
task do_something();
@ (posedge signal);
forever begin : restart
fork
forever begin : f_loop
wait_some_time;
act;
@ (posedge signal);
end : f_loop
@ (posedge signal);
join_any
disable f_loop; // or disable fork; if this is an isolated fork
end : restart
endtask
Thanks Dave and ABD