Added StopWatch example for DOM and documentation testing.

1 files changed, 58 insertions, 0 deletions

diff --git a/testsuite/pyunit/dom/examples/StopWatch/Debouncer.vhdl b/testsuite/pyunit/dom/examples/StopWatch/Debouncer.vhdl
new file mode 100644
index 000000000..18207c7f1
--- /dev/null
+++ b/testsuite/pyunit/dom/examples/StopWatch/Debouncer.vhdl
@@ -0,0 +1,58 @@
+-- Author:  Patrick Lehmann
+-- License: MIT
+--
+-- A generic counter module used in the StopWatch example.
+--
+library IEEE;
+use     IEEE.std_logic_1164.all;
+use     IEEE.numeric_std.all;
+
+use     work.Utilities.all;
+
+
+entity Debouncer is
+	generic (
+		CLOCK_PERIOD   : time := 10 ns;
+		DEBOUNCE_TIME  : time := 3 ms;
+
+		BITS           : positive
+	);
+	port (
+		Clock  : in  std_logic;
+
+		Input  : in  std_logic_vector(BITS - 1 downto 0);
+		Output : out std_logic_vector(BITS - 1 downto 0) := (others => '0')
+	);
+end entity;
+
+architecture rtl of Debouncer is
+	constant DEBOUNCE_COUNTER_MAX  : positive := DEBOUNCE_TIME / (CLOCK_PERIOD* ite(IS_SIMULATION, 20, 1));
+	constant DEBOUNCE_COUNTER_BITS : positive := log2(DEBOUNCE_COUNTER_MAX);
+
+begin
+	assert false report "CLOCK_PERIOD:         " & time'image(CLOCK_PERIOD);
+	assert false report "DEBOUNCE_TIME:        " & time'image(DEBOUNCE_TIME);
+	--assert false report "DEBOUNCE_COUNTER_MAX: " & to_string(10 ns);
+	--assert false report "INTEGER'high:         " & integer'image(integer'high);
+
+	genBits: for i in Input'range generate
+		signal DebounceCounter         : signed(DEBOUNCE_COUNTER_BITS downto 0) := to_signed(DEBOUNCE_COUNTER_MAX - 3, DEBOUNCE_COUNTER_BITS + 1);
+	begin
+		process (Clock)
+		begin
+			if rising_edge(Clock) then
+				-- restart counter, whenever Input(i) was unstable within DEBOUNCE_TIME_MS
+				if (Input(i) /= Output(i)) then
+					DebounceCounter <= DebounceCounter - 1;
+				else
+					DebounceCounter <= to_signed(DEBOUNCE_COUNTER_MAX - 3, DebounceCounter'length);
+				end if;
+
+				-- latch input bit, if input was stable for DEBOUNCE_TIME_MS
+				if (DebounceCounter(DebounceCounter'high) = '1') then
+					Output(i) <= Input(i);
+				end if;
+			end if;
+		end process;
+	end generate;
+end architecture;