Mechanics of Local Variables - SVA: The Power of Assertions in SystemVerilog - page 358

sequence s_arg_dirs(

1

local input byte l_s_i,

2

local inout byte l_s_io,

3

local output byte l_s_o

4

);

5

... // l_s_o must be assigned in the body

6

endsequence

7

8
9

property p_arg_dirs;

byte l_p_io, l_p_o;

10

(start, l_p_io = e_io)

11

|-> s_arg_dirs(e_i, l_p_io, l_p_o)

12

|-> results_ok(l_p_io, l_p_o);

13

endproperty

14

Fig. 16.3 Sequence with argument local variables of all directions

its initial value from l_p_io , which is assigned the value of e_io in Line 11 . l_s_o
gets no initial value. Whenever s_arg_dirs matches, the values of l_s_io and
l_s_o are output to l_p_io and l_p_o , respectively, and these values are used in
the check of results_ok in Line 13 . Further details on output and inout argument
local variables will be discussed in Sect. 16.5 .
The following rules apply in declaration of argument local variables: If a
direction is specified for an argument, then the keyword local must also be
specified, and if the keyword local is specified, then the data type must be explicitly
specified, including any packed dimensions. Unpacked dimensions may also be
specified. Since the arguments of s_arg_dirs have distinct directions, they must
each specify the keyword local and therefore must also repeat the data type byte .
It is allowed to specify the keyword local without a direction, and in this
case the direction input is understood. Thus, the following variant is semantically
equivalent to s_arg_dirs :
sequence s_arg_dirs_v2(
local byte l_s_i,
local inout byte l_s_io,
local output byte l_s_o

);

...
endsequence
Consecutive declarations of argument local variables can share the same specifi-
cations of the keyword local , the direction, and the data type (including any packed
dimensions), but only if the following conditions are satisfied:
1. The first of the declarations specifies local , specifies the direction either
explicitly or implicitly, explicitly specifies the data type (including any packed
dimensions), and does not specify any unpacked dimensions.
2. Subsequent declarations specify only the formal argument identifier. No
packed or unpacked dimensions may be specified together with the subsequent
identifiers.