From a04bbf15b0f51696894e37f3e566998108aefd74 Mon Sep 17 00:00:00 2001
From: Johann Faerber <johann.faerber@hs-augsburg.de>
Date: Wed, 9 Mar 2022 09:48:43 +0100
Subject: added basic design directory structure

---
 src/mux2to1_truthtable.vhd | 54 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 src/mux2to1_truthtable.vhd

(limited to 'src/mux2to1_truthtable.vhd')

diff --git a/src/mux2to1_truthtable.vhd b/src/mux2to1_truthtable.vhd
new file mode 100644
index 0000000..ff84c61
--- /dev/null
+++ b/src/mux2to1_truthtable.vhd
@@ -0,0 +1,54 @@
+-------------------------------------------------------------------------------
+-- Module     : mux2to1
+-------------------------------------------------------------------------------
+-- Author     : Johann Faerber
+-- Company    : University of Applied Sciences Augsburg
+-------------------------------------------------------------------------------
+-- Description: 2-to-1 multiplexer
+--              function modelled by a truth table
+--              sel = '1': a -> y
+--              sel = '0': b -> y
+-------------------------------------------------------------------------------
+-- Revisions  : see end of file
+-------------------------------------------------------------------------------
+LIBRARY IEEE;
+USE IEEE.std_logic_1164.ALL;
+
+ENTITY mux2to1 IS
+  PORT (a_i   : IN  std_ulogic;       -- data input a
+        b_i   : IN  std_ulogic;       -- data input b
+        sel_i : IN  std_ulogic;       -- select which input is connected to y
+                                      -- sel = '1': a -> y
+                                      -- sel = '0': b -> y
+        y_o   : OUT std_ulogic        -- data output y
+        );
+END mux2to1;
+
+ARCHITECTURE truthtable OF mux2to1 IS
+
+  SIGNAL inputs_s : std_ulogic_vector(2 DOWNTO 0);  -- temp input vector
+  
+BEGIN
+  
+  inputs_s <= (sel_i, b_i, a_i); -- concatenate single signals to a vector
+  
+  tt : WITH inputs_s SELECT      -- truthtable 
+    y_o <=
+    '0' WHEN "000",
+    '0' WHEN "001",
+    '1' WHEN "010",
+    '1' WHEN "011",
+    '0' WHEN "100",
+    '1' WHEN "101",
+    '0' WHEN "110",
+    '1' WHEN "111",
+    'X' WHEN OTHERS;
+
+END truthtable;
+
+-------------------------------------------------------------------------------
+-- Revisions:
+-- ----------
+-- $Id:$
+-------------------------------------------------------------------------------
+
-- 
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