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library ieee ;
use ieee.std_logic_1164.std_logic ;
use ieee.std_logic_1164.std_ulogic ;
use ieee.std_logic_1164."not";
package frequency is
type frequency is range 0 to 2e9 units
Hz ;
kHz = 1000 Hz ;
MHz = 1000 kHz ;
GHz = 1000 MHz ;
THz = 1000 GHz ;
end units ;
function half_period(freq : frequency) return time ;
function period(freq : frequency) return time ;
-- GHDL workaround to make a generic package and instantiate it?
package gen_generate_clock is
generic (
type t ;
function "not"(x : t) return t is <>
) ;
procedure generate_clock(signal clock : inout t ; freq : frequency ; count : natural := 0) ;
end package ;
package generate_clock_bit is new gen_generate_clock generic map(t => bit) ;
package generate_clock_std_logic is new gen_generate_clock generic map(t => std_logic) ;
package generate_clock_std_ulogic is new gen_generate_clock generic map(t => std_ulogic) ;
alias generate_clock is generate_clock_bit.generate_clock[bit, frequency, natural] ;
alias generate_clock is generate_clock_std_logic.generate_clock[std_logic, frequency, natural] ;
-- Dedeclaration?
--alias generate_clock is generate_clock_std_ulogic.generate_clock[std_ulogic, frequency, natural] ;
-- Doesn't work in GHDL
--procedure generate_clock generic (
-- type t ;
-- function "not"(x : t) return t is <>
--) parameter (signal clock : inout t ; freq : frequency ; count : natural := 0) ;
--procedure generate_clock is new generate_clock generic map(t => std_ulogic) ;
--procedure generate_clock is new generate_clock generic map(t => std_logic) ;
--procedure generate_clock is new generate_clock generic map(t => bit) ;
end package ;
package body frequency is
function period(freq : frequency) return time is
begin
return 1 sec / frequency'pos(freq) ;
end function ;
function half_period(freq : frequency) return time is
begin
return period(freq) / 2.0 ;
end function ;
package body gen_generate_clock is
procedure generate_clock(
signal clock : inout t ;
freq : frequency ;
count : natural := 0
) is
constant hp : time := half_period(freq) ;
variable downcount : natural := count ;
begin
-- count = 0 means forever, otherwise we look at the downcount
while count = 0 or downcount > 0 loop
clock <= not clock after hp ;
downcount := downcount - 1 ;
end loop ;
end procedure ;
end package body ;
--procedure generate_clock generic(
-- type t ;
-- function "not"(x : t) return t is <>
--) parameter (
-- signal clock : inout t ;
-- freq : frequency ;
-- count : natural := 0
--) is
-- constant hp : time := half_period(freq) ;
-- variable downcount : natural := count ;
--begin
-- -- count = 0 means forever, otherwise we look at the downcount
-- while count = 0 or downcount > 0 loop
-- clock <= not clock after hp ;
-- downcount := downcount - 1 ;
-- end loop ;
--end procedure ;
end package body ;
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