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# help with incrementors

Lilmiss
Guest
Posts: n/a

 07-19-2005
If anyone provide me with vhdl source code for any of the following:
1) Design a circuit that increments a 4-bit number A3A2A1A0 by 1. In a
similar manner to the adder circuit, start by designing a 1-bit
incrementer circuit.
2)Write a behavioral-style VHDL code for a 1-bit incrementor circuit as
described in Problem 2. Then write a structural-style VHDL code for an
8-bit incrementor using generate statements. Write a testbench to simulate
your design
3)Write VHDL code for an n-bit incrementor circuit. Write a testbench to
simulate your incrementor for n=16, 32, and 64.

Thanks in advance!

Mike Treseler
Guest
Posts: n/a

 07-19-2005
Lilmiss wrote:

> 2)Write a behavioral-style VHDL code for a 1-bit incrementor circuit as
> described in Problem 2.

n := n + 1;

Check the back of the book for the odd numbered problems.

-- Mike Treseler

Ralf Hildebrandt
Guest
Posts: n/a

 07-19-2005
Lilmiss wrote:

> If anyone provide me with vhdl source code for any of the following:
> 1) Design a ...

> Thanks in advance!

We will help you with your homework, if you show a certain amount of own
work and are trapped by a (small) error.

I will suggest only one thing:

library IEEE;
use IEEE.numeric_std.all;

This provides arithmetic operations on unsigned and signed vectors.

Ralf

Lilmiss
Guest
Posts: n/a

 07-23-2005
Hi again,

Well I tried working on them again, but I'm still stuck at the last
question. I managed to write this code...Could you provide any suggestions
for improving it?

Generate:

library IEEE;
use IEEE.STD_LOGIC_1164.all;

Entity incrementer_st is
generic(width : positive);
port(A : in std_logic_vector (width-1 downto 0) ;
C0 : in std_logic;
Cn : out std_logic;
S : out std_logic_vector(width-1 downto 0));
End incrementer_st;

architecture incrementer_st of incrementer_st is
component incrementer
port ( A : in STD_LOGIC;
Cin : in STD_LOGIC;
S : out STD_LOGIC;
Cout : out STD_LOGIC);
end component;
signal C : std_logic_vector(0 to width);
begin
g1 : for b in 0 to width-1 generate
U1: incrementer port map(A=>A(b), Cin=> C(b), S=>S(b), Cout=>C(b+1));
end generate;

C(0) <= C0;
Cn <= C(width);
end incrementer_st;

--Also, could you clarify the difference between generic and generate
statements (silly question I know)

10x

james
Guest
Posts: n/a

 07-25-2005
On Sat, 23 Jul 2005 13:28:40 -0400, "Lilmiss"
<(E-Mail Removed)> wrote:

>+<Hi again,
>+<
>+<Well I tried working on them again, but I'm still stuck at the last
>+<question. I managed to write this code...Could you provide any suggestions
>+<for improving it?
>+<
>+<
>+<Generate:
>+<
>+< library IEEE;
>+<use IEEE.STD_LOGIC_1164.all;
>+<
>+<
>+<Entity incrementer_st is
>+< generic(width : positive);

******

First off you have declared width and assigned an attribute but no
value has been assigned. How wide is width? 5 bits, 15 bits, 32 bits?

>+< port(A : in std_logic_vector (width-1 downto 0) ;
>+< C0 : in std_logic;
>+< Cn : out std_logic;
>+< S : out std_logic_vector(width-1 downto 0));
>+< End incrementer_st;
>+<
>+<
>+<
>+<architecture incrementer_st of incrementer_st is

******

What are you trying to do with the code below?
Instantiate or describe an architecture?

>+<component incrementer
>+<port ( A : in STD_LOGIC;
>+<Cin : in STD_LOGIC;
>+<S : out STD_LOGIC;
>+<Cout : out STD_LOGIC);
>+<end component;
>+<signal C : std_logic_vector(0 to width);
>+<begin
>+< g1 : for b in 0 to width-1 generate
>+< U1: incrementer port map(A=>A(b), Cin=> C(b), S=>S(b), Cout=>C(b+1));
>+< end generate;
>+<
>+< C(0) <= C0;
>+< Cn <= C(width);
>+<end incrementer_st;
>+<
>+<
>+<--Also, could you clarify the difference between generic and generate
>+<statements (silly question I know)
>+<
>+<10x

*******

Generics are used to set default values to signals and ports. They are
declared and assigned in the entity declaration section before port
declarations. An example would be to use generics to set the widths of
busses, bit sizes of registers and others. If you need to change the
widths, you just change the genrics and the rest of the code is
changed. Handy item.

Generate is used to duplicate sections of code or library entities.
Such a case for using generate would be in the creation of a nbit
adder. Your code describes one bit of the adder and then you tell the
synthesizer to duplicate it "n" times.

james

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