rename stopp to abs8b, add comments and cleanup

1 files changed, 29 insertions, 0 deletions

diff --git a/src/abs8b.vhd b/src/abs8b.vhd
new file mode 100644
index 0000000..77b7a25
--- /dev/null
+++ b/src/abs8b.vhd
@@ -0,0 +1,29 @@
+library ieee;
+use ieee.std_logic_1164.all;
+
+entity abs8b is
+	port(
+		A: in std_logic_vector(8 downto 0);
+		X: out std_logic_vector(8 downto 0));
+end abs8b;
+
+architecture Behavioral of abs8b is
+	component twoc
+		port (
+			A: in std_logic_vector(7 downto 0);
+			Cin: in std_logic;
+			X: out std_logic_vector(7 downto 0);
+      Cout: out std_logic);
+	end component;
+	signal ntop: std_logic_vector(8 downto 0);
+begin
+	-- calculate two's complement for A (A * -1)
+	inv: component twoc
+		port map(
+			A => A(7 downto 0),
+			Cin => A(8),
+			X => ntop(7 downto 0),
+			Cout => ntop(8));
+	-- output -A if A < 0 else A
+	X <= ntop when A(8) = '1' else A;
+end Behavioral;