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; //首先这种事件是一个零宽度的脉冲
@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
#解释：
两个initial块同一时刻执行，但即便是在同一时刻运行也有先后顺序，按照书写顺序从上到下运行（试验过两个initial块前后位置调换，结果恰好相反），即，同一时刻事件e1先执行完，在@e2处等待，同时呢，事件e2也被触发，虽然在同一时刻，但由于e1早于e2被触发，所以，后续e2的触发是@e2继续执行，但当到@e1时，由于此时事件e1已经被触发，程序会堵在@e1处。呈现如上log中的结果。