1. Arbitrary Waveform
Discussion 5.5
Example 34

2. Recall Divide-by-8 Counters s s s s s s s
State q2 q1 q D2 D1 D0
Present state Next state
Use q2, q1, q0 as inputs to a combinational circuit
to produce an arbitrary waveform.

3. Example
State q2 q1 q D2 D1 D y q2
q1 q0 00 01 11 10 1 s s s s s s s s
y = ~q2 & ~q1
| q2 & q0

4. International Morse Code

5. Generating a Morse code A using a 3-bit divide-by-8 counter

6. K-map for finding A

7. -- Example 34: Morse code for A
library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.STD_LOGIC_unsigned.all;
entity morsea is
port(
clr : in STD_LOGIC;
clk : in STD_LOGIC;
a : out STD_LOGIC );
end morsea;
architecture morsea of morsea is
signal q: STD_LOGIC_VECTOR(2 downto 0);
begin
-- 3-bit counter
process(clk, clr)
if clr = '1' then
q <= "000";
elsif clk'event and clk = '1' then
q <= q + 1;
end if;
end process;
a <= (not q(1) and q(0)) or (q(2) and not q(0));

8. Aldec Active-HDL Simulation