From c223fc20379554247b348d203d7fc66e68f4e531 Mon Sep 17 00:00:00 2001
From: tmeissner <programming@goodcleanfun.de>
Date: Sat, 2 May 2020 16:55:06 +0200
Subject: [PATCH] Add 4-bit version of sequencer

---
 src/hex_sequencer.vhd | 44 ++++++++++++++++++++++++++++++++++
 src/pkg.vhd           | 56 +++++++++++++++++++++++++++++++++++++++++++
 src/sequencer.vhd     | 12 ++++++----
 3 files changed, 108 insertions(+), 4 deletions(-)
 create mode 100644 src/hex_sequencer.vhd

diff --git a/src/hex_sequencer.vhd b/src/hex_sequencer.vhd
new file mode 100644
index 0000000..ccdda21
--- /dev/null
+++ b/src/hex_sequencer.vhd
@@ -0,0 +1,44 @@
+-- Simple sequencer to generate waveforms for 4 bit std_logic_vector signals
+-- Inspired by SymbioticEDA's sva-demos seq module
+-- https://github.com/SymbioticEDA/sva-demos/blob/master/seq.sv
+
+library ieee;
+  use ieee.std_logic_1164.all;
+
+use work.pkg.all;
+
+
+entity hex_sequencer is
+  generic (
+    seq : string
+  );
+  port (
+    clk  : in  std_logic;
+    data : out std_logic_vector(3 downto 0)
+  );
+end entity hex_sequencer;
+
+
+architecture rtl of hex_sequencer is
+
+  signal cycle : natural := 0;
+  signal ch    : character;
+
+begin
+
+
+  process (clk) is
+  begin
+    if rising_edge(clk) then
+      if (cycle < seq'length) then
+        cycle <= cycle + 1;
+      end if;
+    end if;
+  end process;
+
+  ch <= seq(cycle+1);
+
+  data <= to_hex(ch);
+
+
+end architecture rtl;
diff --git a/src/pkg.vhd b/src/pkg.vhd
index 6ec3b1e..f9127af 100644
--- a/src/pkg.vhd
+++ b/src/pkg.vhd
@@ -15,5 +15,61 @@ package pkg is
     );
   end component sequencer;
 
+  component hex_sequencer is
+    generic (
+      seq : string
+    );
+    port (
+      clk  : in  std_logic;
+      data : out std_logic_vector(3 downto 0)
+    );
+  end component hex_sequencer;
+
+  function to_bit (a : in character) return std_logic;
+  function to_hex (a : in character) return std_logic_vector;
+
 
 end package pkg;
+
+
+package body pkg is
+
+
+  function to_bit (a : in character) return std_logic is
+    variable ret : std_logic;
+  begin
+    case a is
+      when '0' | '_' => ret := '0';
+      when '1' | '-' => ret := '1';
+      when others    => ret := 'X';
+    end case;
+    return ret;
+  end function to_bit;
+
+  function to_hex (a : in character) return std_logic_vector is
+    variable ret : std_logic_vector(3 downto 0);
+  begin
+    case a is
+      when '0' | '_' => ret := x"0";
+      when '1'       => ret := x"1";
+      when '2'       => ret := x"2";
+      when '3'       => ret := x"3";
+      when '4'       => ret := x"4";
+      when '5'       => ret := x"5";
+      when '6'       => ret := x"6";
+      when '7'       => ret := x"7";
+      when '8'       => ret := x"8";
+      when '9'       => ret := x"9";
+      when 'a' | 'A' => ret := x"A";
+      when 'b' | 'B' => ret := x"B";
+      when 'c' | 'C' => ret := x"C";
+      when 'd' | 'D' => ret := x"D";
+      when 'e' | 'E' => ret := x"E";
+      when 'f' | 'F' | '-' => ret := x"F";
+      when others => ret := x"X";
+    end case;
+    return ret;
+  end function to_hex;
+
+
+end package body pkg;
diff --git a/src/sequencer.vhd b/src/sequencer.vhd
index 6b7070c..4ef80cf 100644
--- a/src/sequencer.vhd
+++ b/src/sequencer.vhd
@@ -1,6 +1,12 @@
+-- Simple sequencer to generate waveforms for 1 bit std_logic signals
+-- Inspired by SymbioticEDA's sva-demos seq module
+-- https://github.com/SymbioticEDA/sva-demos/blob/master/seq.sv
+
 library ieee;
   use ieee.std_logic_1164.all;
 
+use work.pkg.all;
+
 
 entity sequencer is
   generic (
@@ -32,9 +38,7 @@ begin
 
   ch <= seq(cycle+1);
 
-  data <= '0' when ch = '0' or ch = '_' else
-          '1' when ch = '1' or ch = '-' else
-          'X';
+  data <= to_bit(ch);
 
 
-end architecture rtl;
\ No newline at end of file
+end architecture rtl;