P
ROCEDURAL
B
LOCKS
P
ROCEDURAL
B
LOCKS
|Behavioral Level Coding is done within
PdlBlkTh tt f
P
roce
d
ura
l
Bl
oc
k
s.
Th
ere are
t
wo
t
ypes o
f
Procedural Block.
y
begin end
y
begin
………………
end
,
,
instr.01 instr.02 #delay instr.03 instr.04
Ti Li
3
Ti
me
Li
ne
t=0 t=delay
3
P
ROCEDURAL
B
LOCKS
(C
ONT
’
D
)
P
ROCEDURAL
B
LOCKS
(C
ONT
D
)
|fork………………join
All i i i hi hi f bl k d
y
All
i
nstruct
i
ons w
i
t
hi
n t
hi
s type o
f
bl
oc
k
are execute
d
in a parallel manner.
#delay
,
instr.02 instr.04
,
instr.01 instr.03
Time Line
t=0 t=delay
4
4
EXAMPLE:
Wh t th fi l l f i
module iaf1;
integer i, j;
initial begin
Wh
a
t
are
th
e
fi
na
l
va
l
ues o
f
i
and j?
At t=0 i and j are assigned values 3 & 4
initial
begin
i = 3;
j = 4;
fork
At
t=0
,
i
and
j
are
assigned
values
3
&
4
respectively.
Then program enters the fork-join block. At
t
=
1, i and j are sampled and assigned new
#1 i = j;
#1 j = i;
join
t1,
i
and
j
are
sampled
and
assigned
new
,
end
endmodule module iaf1 ;
integer i, j;
iiilb i
,
How to solve this issue?
i
n
i
t
i
a
l
b
eg
i
n
i = 3;
j = 4;
fork
Intra-
Assignmen
t Delay
Using Intra-Assignment
Delays.
fork
#1 i = #1 j;
#1 j = #1 i;
join
5
join
end
endmodule
5
PROCEDURA
L
A
SSIGNMENT
|Data types reg, integer, real and time can only
be assigned a value in Procedural Blocks.
be
assigned
a
value
in
Procedural
Blocks.
These statements are called Procedural
Assignment Statements.module ianb;
integer i j;
• Procedural Assignment
Statements can be classified as:
integer
i
,
j;
,
¾Blocking Procedural Assignment:
• Instructions are executed in a
se
q
uential manner.
i = #1 j;
j = #1 i;
end
end
e
n
d
m
odu
l
e
,
q
¾NonBlocking Procedural
Assignment:
e d odu e
module ianb;
integer i, j;
initial begin
• RHS of all these assignment
statements (Sampling) is done at
t=0. After then at the specified delay
S
i = 3;
j = 4;
begin
i < = #1 j;
j<
=
#1 i;
6
they are assigned to LH
S
.
j
<
#1
i;
end
end
endmodule
6
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