starting files and example programs

1 files changed, 51 insertions, 0 deletions

diff --git a/PIC/stack.vhd b/PIC/stack.vhd
new file mode 100644
index 0000000..fd376c0
--- /dev/null
+++ b/PIC/stack.vhd
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+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity stack is
+  generic (
+    DEPTH : positive := 8;
+    WIDTH : positive := 13
+  );
+  port (
+    clk   : in  std_logic;
+    reset : in  std_logic;
+    push  : in  std_logic;
+    pop   : in  std_logic;
+    din   : in  std_logic_vector(WIDTH - 1 downto 0);
+    dout  : out std_logic_vector(WIDTH - 1 downto 0)
+  );
+end entity stack;
+
+architecture rtl of stack is
+
+  type stack_t is
+    array (0 to DEPTH - 1)
+    of std_logic_vector(WIDTH - 1 downto 0);
+
+  signal mem : stack_t
+    := (others => (others => '0'));
+
+  -- write pointer
+  signal top : unsigned(2 downto 0)
+    := (others => '0');
+begin
+
+  dout <=
+    mem(to_integer(top - 1)) when top /= 0 else (others => '0');
+
+  stck : process(clk, reset)
+  begin
+    if reset = '1' then
+      top <= (others => '0');
+    elsif rising_edge(clk) then
+      if push = '1' then
+        mem(to_integer(top)) <= din;
+        top                  <= top + 1;
+      elsif pop = '1' then
+        top <= top - 1;
+      end if;
+    end if;
+  end process;
+
+end architecture rtl;