| 范例：opencore组织RISCMCU IP Core全套最新代码 _pc | ----------------------------------------------------------------------------
---- ----
---- WISHBONE RISCMCU IP Core ----
---- ----
---- This file is part of the RISCMCU project ----
---- http://www.opencores.org/projects/riscmcu/ ----
---- ----
---- Description ----
---- Implementation of a RISC Microcontroller based on Atmel AVR ----
---- AT90S1200 instruction set and features with Altera Flex10k20 FPGA. ----
---- ----
---- Author(s): ----
---- - Yap Zi He, yapzihe@hotmail.com ----
---- ----
----------------------------------------------------------------------------
---- ----
---- Copyright (C) 2001 Authors and OPENCORES.ORG ----
---- ----
---- This source file may be used and distributed without ----
---- restriction provided that this copyright statement is not ----
---- removed from the file and that any derivative work contains ----
---- the original copyright notice and the associated disclaimer. ----
---- ----
---- This source file is free software; you can redistribute it ----
---- and/or modify it under the terms of the GNU Lesser General ----
---- Public License as published by the Free Software Foundation; ----
---- either version 2.1 of the License, or (at your option) any ----
---- later version. ----
---- ----
---- This source is distributed in the hope that it will be ----
---- useful, but WITHOUT ANY WARRANTY; without even the implied ----
---- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ----
---- PURPOSE. See the GNU Lesser General Public License for more ----
---- details. ----
---- ----
---- You should have received a copy of the GNU Lesser General ----
---- Public License along with this source; if not, download it ----
---- from http://www.opencores.org/lgpl.shtml ----
---- ----
----------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity v_pc is
port( offset : in std_logic_vector(8 downto 0);
en, addoffset, push, pull, vec2, vec4 : in std_logic;
clk, clrn : in std_logic;
pc : buffer std_logic_vector(8 downto 0)
);
end v_pc;
architecture pc of v_pc is
constant vector2 : std_logic_vector(8 downto 0) := "000000001";
constant vector4 : std_logic_vector(8 downto 0) := "000000010";
signal pcb, stack0, stack1, stack2, stack3 : std_logic_vector(8 downto 0);
begin
process(clk, clrn)
begin
if clrn = '0' then
pc <= "000000000";
pcb <= "000000000";
stack0 <= "000000000";
stack1 <= "000000000";
stack2 <= "000000000";
stack3 <= "000000000";
elsif clk'event and clk = '1' then
if en = '1' then
pcb <= pc;
if addoffset = '1' then
pc <= pcb + offset;
elsif pull = '1' then
pc <= stack0;
elsif vec2 = '1' then
pc <= vector2;
elsif vec4 = '1' then
pc <= vector4;
else
pc <= pc + 1;
end if;
if push = '1' then
if addoffset = '1' then
stack0 <= pcb;
else
stack0 <= pcb - 1;
end if;
stack1 <= stack0;
stack2 <= stack1;
stack3 <= stack2;
elsif pull = '1' then
stack0 <= stack1;
stack1 <= stack2;
stack2 <= stack3;
end if;
end if;
end if;
end process;
end pc;
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