you would not usually infer registers from them directly, just how they are used.
If they are used inside a clocked process, then assuming they synthesise, they will infer registered logic. Technically here, the function/procedure have only infered logic, with the clocked process infering the register.
A function can NEVER infer a register on it's own, because a function cannot have timing inside it, and it always completes within a single delta.
But I believe it is possible to infer a register from a procedure. For example, the following procedures should infer a register when compiled:
| Code VHDL - [expand] |
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| procedure reg(signal clk : in std_logic;
signal d : in std_logic;
signal q : out std_logic ) is
begin
if rising_edge(clk) then
q <= d;
end if;
end procedure;
-- this should also infer a register (if synth tool supports wait until in process, which most do if there is only 1)
procedure reg(signal clk : in std_logic;
signal d : in std_logic;
signal q : out std_logic ) is
begin
wait until rising_edge(clk);
q <= d;
end procedure;
...
architecture rtl of my_ent is
begin
reg(clk, ent_ip, ent_op);
end architecture rtl; |
This works because code not inside a process actually infer a process, sensitive to all "input" signals.
so this line:
a <= b;
is actually this process:
Code:
process(b)
begin
a <= b;
end process;