1. Digital Design with VHDL Presented by: Amir Masoud Gharehbaghi Email: amgh@mehr.sharif.edu

2. Concurrent Statements Concurrent Signal Assignment Component Instantiation Statement Generate Statement Process Statement Block Statement Concurrent Procedure Call Statement Concurrent Assert Statement

3. Sequential Statements Signal Assignment Statement Variable Assignment Statement IF Statement Case Statement Loop Statement Wait Statement Procedure Call Statement

4. Sequential Statements (cont.) Next Statement Exit Statement Return Statement Assertion Statement Report Statement Null Statement

5. Serial to Parallel (Entity) ENTITY s2p IS GENERIC (bps: INTEGER); PORT (s_in, rec : IN BIT; d_ready: BUFFER BIT; overrun, f_error: OUT BIT; p_out: OUT BIT_VECTOR(7 DOWNTO 0)); END s2p;

6. Serial to Parallel ARCHITECTURE w OF s2p IS BEGIN collect: PROCESS VARIABLE buff: BIT_VECTOR(7 DOWNTO 0); CONSTANT half: TIME :=(1000000.0/REAL(bps))/2.0*1 US; CONSTANT full: TIME :=(1000000.0/REAL(bps))/2.0*1 US; BEGIN WAIT UNTIL serial = ‘ 0 ’ ; WAIT FOR half; FOR count IN 0 TO 7 LOOP WAIT FOR full; buff(count) := serail; END LOOP;

7. Serial to Parallel IF serial = ‘ 0 ’ THEN f_error <= ‘ 1 ’ ; WAIT UNTIL serial = ‘ 1 ’ ; ELSE f_errro <= ‘ 0 ’ ; d_ready <= ‘ 1 ’ ; p_out <= buff; WAIT UNTIL rec = ‘ 1 ’ ; WAIT UNTIL rec = ‘ 0 ’ ; d_ready <= ‘ 0 ’ ; END IF; END PROCESS;

8. Serial to Parallel too_fast: PROCESS BEGIN IF d_ready = ‘ 1 ’ THEN WAIT UNTIL serial = ‘ 0 ’ ; IF d_ready = ‘ 1 ’ THEN overrun <= ‘ 1 ’ ; END IF; ELSE overrun <= ‘ 0 ’ ; END IF; WAIT ON d_ready; END PROCESS; END w;

9. Enumeration Type Declaration TYPE identifier IS (enumeration_literal {, enumeration_literal } ); enumeration_literal ::= identifier | character_literal

10. Moore FSM ENTITY moore IS PORT (x, clk: IN BIT; z: OUT BIT); END moore; ARCHITECTURE behavioral OF moore IS TYPE state IS (reset,got1,got10,got101,got1011); SIGNAL current : state := reset; BEGIN

11. Moore FSM (cont.) PROCESS BEGIN WAIT UNTIL clk = ‘ 1 ’ ; CASE current IS WHEN reset => IF x = ‘ 0 ’ THEN current <= got1; ELSE current <= reset; END IF; … END CASE; END PROCESS; z <= ‘ 1 ’ WHEN current = got1011 ELSE ‘ 0 ’ ; END behavioral;

12. Mealy FSM ARCHITECTURE behavioral OF mealy IS TYPE state IS (a, b, c); SIGNAL nxt, present : state := a; BEGIN -- of architecture PROCESS (clk) BEGIN IF (clk ’ EVENT AND clk = ‘ 1 ’ ) THEN present <= nxt; END IF; END PROCESS;

13. Mealy FSM (cont.) PROCESS (present, x) BEGIN z <= ‘ 0 ’ ; CASE present IS WHEN a => IF x = ‘ 0 ’ THEN nxt <= a ELSE nxt <= b; END IF; … END CASE; IF present = c AND x = ‘ 1 ’ THEN z <= ‘ 1 ’ ; END IF; END PROCESS; END behavioral ; -- of architecture

14. Array Type Declaration TYPE identifier IS ARRAY ( index {, index} ) OF element_subtype; Index ::= range | NATURAL RANGE <>

15. Array Type Example TYPE BIT_VECTOR IS ARRAY (NATURAL RANGE <>) OF BIT; TYPE two_dim_bit IS ARRAY (0 TO 7, 15 DOWNTO 0) OF BIT; TYPE byte_memory IS ARRAY (NATURAL RANGE <>) OF BIT_VECTOR (7 DOWNTO 0);

16. Signal of Array Type Example SIGNAL a: BIT_VECTOR(1 TO 16); SIGNAL b: two_dim_bit; SIGNAL c: byte_memory(0 TO 1023); … c(0) <= a(1 TO 8); a(1 TO 8) <= b(1,15)&b(1,14)&b(1,13)&b(1,12)&b(1,11)&b(1,10) &b(1,9)&b(1,8); c(0) <= a(5 TO 12);

17. Specifying Radix SIGNAL a: BIT_VECTOR(7 DOWNTO 0); SIGNAL b: INTEGER;.. aa <= "10101111", B"0111_0101" AFTER 10 ns, x"F1" AFTER 50 ns; bb <= 100_789, 16#3F7# AFTER 30 NS, 4#103_2122# AFTER 100 ns;