一、SV中非阻塞事件
module test;
event ev1, ev2;//belong to logic function part
always@(ev1)
$display("ev1 triggered at %0ts", $time);
initial wait(ev2.triggered)
$display("ev2 triggered at %0ts", $time);
//belong to stimulus
initial begin
->> #5 ev1; //"->>": non-blocking event, delay 5 cycle triggering the event
end
initial begin
->> @(ev1) ev2; //event ev1 and ev2 will triggered simutaneous,but ev1 is earlier.
end
endmodule
//Makefile
comp:
vcs -sverilog Synchronous multi-events.sv -l comp.log
run:
./simv -l run.log
clean:
\rm -rf csrc simv* *.log
//run.log
ev1 triggered at 5s
ev2 triggered at 5s
//--------------------------------------------------------------------------------------------------------------
二、SV中阻塞事件
program p;
event e1, e2;
initial begin
$display("@%0t: 1: before trigger", $time);
->e1; //首先這種事件是一個零寬度的脈衝
@e2;
$display("@%0t: 1: after trigger", $time);
end
initial begin
$display("@%0t: 2: before trigger", $time);
->e2;
@e1;
$display("@%0t: 2: after trigger", $time);
end
endprogram
//Makefile
comp:
vcs -sverilog *..sv -l comp.log
run:
./simv -l run.log
clean:
\rm -rf csrc simv* *.log
//run.log
@0: 1: before trigger
@0: 2: before trigger
@0: 1: after trigger
#解釋：
兩個initial塊同一時刻執行，但即便是在同一時刻運行也有先後順序，按照書寫順序從上到下運行（試驗過兩個initial塊前後位置調換，結果恰好相反），即，同一時刻事件e1先執行完，在@e2處等待，同時呢，事件e2也被觸發，雖然在同一時刻，但由於e1早於e2被觸發，所以，後續e2的觸發是@e2繼續執行，但當到@e1時，由於此時事件e1已經被觸發，程序會堵在@e1處。呈現如上log中的結果。