Changes
PWM
,Pulse Width Modulation, is a DAC (Digital Analog Convertor) using only numerical components (outputting only 0v or 5v values)<br />
Using an entry clock, you output several signals 0v or 5v in order to result an average fix value between 0v and 5v, for sample 2.3v. Changing like it the speed of a small electric motor (speeding it up or slowing it down) as you want but using at input its inputs only two values : 0v or 5v.<br />
Using a quicker clock, you can generate analog signal, like sound music.
entity PWM is
port (
clk : in std_logic;-- 1MHz : same one as sound chip clk
PWM_in : in std_logic_vector (7 downto 0) := "00000000";
PWM_out : out std_logic
end PWM_arch;
Ok, let's go further, let's target 2.5v using only 0v and 5v, with a stupid slow clock, you result in a sequence like this : 05050505050505v. It has a bad border effect : it 's a noise ! 2.5v normaly doesn't produce sound by here, but using this simple PWM it does.<br />
This problem is solved here : this is an original homemade PWM component enabling Arkanoid not producing noises instead of silents, don't ask me how I solved it two years ago but it does :
-- {@ {@{@{@{@ {@ CoreAmstrad is implementation of FPGAmstrad on MiST-board
-- {@{@ {@{@ Contact : renaudhelias@gmail.com
-- {@{@{@{@{@{@{@{@ @see httpshttp://github.com/mist-devel/mist-board/wiki
-- {@{@{@{@{@{@ @see FPGAmstrad at CPCWiki
--
entity PWM is
port (
clk : in std_logic;-- 50MHz : higher than dog and cat frequency, a multiple of clk_ref clk_ref : in std_logic;-- 1MHz : same one as sound chip clk
PWM_in : in std_logic_vector (7 downto 0) := "00000000";
PWM_out : out std_logic
PWM_out <= PWM_Accumulator(8);
end PWM_arch;
[[Category:Hardware]]
