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about describe combinational logic in alway block

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gentle_man

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to use blocking and non-blocking assignment in always construct to describe a combinatioanl logic, the following 2 methods do work, but which is the better, and why
for example, adder

always(...)
out <= in1 + in2;

always(...)
out = in1 + in2;

thanks
 

I think they are same.
 

Hi gentle_man,

Normally, use of nonblocking assignments in place of blocking assignments is highly recommended in RTL design.
 

Hi
Usually, blocking assignments are recommended for modelling combinational circuits and non-blocking assignments to model seqential circuits.
 

Hello!!
It are examples identical.
Blocking and non-blocking assignment
always @(...)
begin
A=B;
C=A;
D=C;
end

result - D=B, C=B and A=B

always @(...)
begin
A<=B;
C<=A;
D<=C;
end

result - D=C(before), C=A(before) and A=B
 

If it is a purely combinatorial circuit they have exactly the same effect.
However, with non-blocking the always block is executed 3 times, while with blocking just once, so I guess there is a perfomance advantage in using blocking statements
 

if u consider intra delays ...there is lots of difference n r u considering all variables in sensitivity list?
 

no acceptable for synthesis tools , to obey RTL design rule, using non-block in sequence logic and using block in combinational logic, else you will meet unnecessary problem.
 

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