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-- Copyright (C) 2002 Morgan Kaufmann Publishers, Inc
-- This file is part of VESTs (Vhdl tESTs).
-- VESTs is free software; you can redistribute it and/or modify it
-- under the terms of the GNU General Public License as published by the
-- Free Software Foundation; either version 2 of the License, or (at
-- your option) any later version.
-- VESTs 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 General Public License
-- for more details.
-- You should have received a copy of the GNU General Public License
-- along with VESTs; if not, write to the Free Software Foundation,
-- Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
package cpu_types is
constant word_size : positive := 16;
subtype word is bit_vector(word_size - 1 downto 0);
type status_value is ( halted, idle, fetch, mem_read, mem_write,
io_read, io_write, int_ack );
end package cpu_types;
package bit_vector_unsigned_arithmetic is
function "+" ( bv1, bv2 : bit_vector ) return bit_vector;
end package bit_vector_unsigned_arithmetic;
package body bit_vector_unsigned_arithmetic is
function "+" ( bv1, bv2 : bit_vector ) return bit_vector is
alias norm1 : bit_vector(1 to bv1'length) is bv1;
alias norm2 : bit_vector(1 to bv2'length) is bv2;
variable result : bit_vector(1 to bv1'length);
variable carry : bit := '0';
begin
if bv1'length /= bv2'length then
report "arguments of different length" severity failure;
else
for index in norm1'reverse_range loop
result(index) := norm1(index) xor norm2(index) xor carry;
carry := ( norm1(index) and norm2(index) )
or ( carry and ( norm1(index) or norm2(index) ) );
end loop;
end if;
return result;
end function "+";
end package body bit_vector_unsigned_arithmetic;
-- code from book
package DMA_controller_types_and_utilities is
alias word is work.cpu_types.word;
alias status_value is work.cpu_types.status_value;
alias "+" is work.bit_vector_unsigned_arithmetic."+"
[ bit_vector, bit_vector return bit_vector ];
-- . . .
end package DMA_controller_types_and_utilities;
-- end code from book
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