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microwatt/writeback.vhdl

112 lines
2.7 KiB
VHDL

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.common.all;
entity writeback is
port (
clk : in std_ulogic;
e_in : in Execute2ToWritebackType;
l_in : in Loadstore2ToWritebackType;
m_in : in MultiplyToWritebackType;
w_out : out WritebackToRegisterFileType;
c_out : out WritebackToCrFileType;
complete_out : out std_ulogic
);
end entity writeback;
architecture behaviour of writeback is
type reg_internal_type is record
complete : std_ulogic;
end record;
type reg_type is record
w : WritebackToRegisterFileType;
c : WritebackToCrFileType;
end record;
signal r, rin : reg_type;
signal r_int, rin_int : reg_internal_type;
begin
writeback_0: process(clk)
begin
if rising_edge(clk) then
r <= rin;
r_int <= rin_int;
end if;
end process;
writeback_1: process(all)
variable x: std_ulogic_vector(0 downto 0);
variable y: std_ulogic_vector(0 downto 0);
variable z: std_ulogic_vector(0 downto 0);
variable v : reg_type;
variable v_int : reg_internal_type;
begin
v := r;
v_int := r_int;
x := "" & e_in.valid;
y := "" & l_in.valid;
z := "" & m_in.valid;
assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1;
x := "" & e_in.write_enable;
y := "" & l_in.write_enable;
z := "" & m_in.write_reg_enable;
assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1;
assert not(e_in.write_cr_enable = '1' and m_in.write_cr_enable = '1');
v.w := WritebackToRegisterFileInit;
v.c := WritebackToCrFileInit;
v_int.complete := '0';
if e_in.valid = '1' or l_in.valid = '1' or m_in.valid = '1' then
v_int.complete := '1';
end if;
if e_in.write_enable = '1' then
v.w.write_reg := e_in.write_reg;
v.w.write_data := e_in.write_data;
v.w.write_enable := '1';
end if;
if e_in.write_cr_enable = '1' then
v.c.write_cr_enable := '1';
v.c.write_cr_mask := e_in.write_cr_mask;
v.c.write_cr_data := e_in.write_cr_data;
end if;
if l_in.write_enable = '1' then
v.w.write_reg := l_in.write_reg;
v.w.write_data := l_in.write_data;
v.w.write_enable := '1';
end if;
if m_in.write_reg_enable = '1' then
v.w.write_enable := '1';
v.w.write_reg := m_in.write_reg_nr;
v.w.write_data := m_in.write_reg_data;
end if;
if m_in.write_cr_enable = '1' then
v.c.write_cr_enable := '1';
v.c.write_cr_mask := m_in.write_cr_mask;
v.c.write_cr_data := m_in.write_cr_data;
end if;
-- Update registers
rin <= v;
rin_int <= v_int;
-- Update outputs
complete_out <= r_int.complete;
w_out <= r.w;
c_out <= r.c;
end process;
end;