School of Engineering Themen: Variablen Architecture-Types.

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1 School of Engineering Themen: Variablen Architecture-Types

2 School of Engineering Variablen

3 School of Engineering Abstimmanlage: version-A LIBRARY ieee; USE ieee.std_logic_1164.all; ENTITY abstimm IS PORT ( a,b,c : in std_logic; y: out std_logic); END abstimm; ARCHITECTURE comb OF abstimm IS BEGIN y <= (a and b) or (a and c) or (b and c); END comb;

4 School of Engineering Abstimmanlage: version-B LIBRARY ieee; USE ieee.std_logic_1164.all; ENTITY abstimm_whenelse IS PORT ( a,b,c : in std_logic; y: out std_logic); END abstimm_whenelse; ARCHITECTURE comb OF abstimm_whenelse IS SIGNAL x : std_logic_vector (2 DOWNTO 0); BEGIN x <= a & b & c; y <= '1' WHEN ((x="011") or (x="101") or (x="110") or (x="111")) ELSE '0'; END comb;

5 School of Engineering Abstimmanlage: version-C ARCHITECTURE rtl OF abstimm_case IS BEGIN comb_log : process(a,b,c) variable x : std_logic_vector (2 DOWNTO 0); BEGIN x := a & b & c; CASE x IS WHEN "011" => y <= '1'; WHEN "101" => y <= '1'; WHEN "110" => y <= '1'; WHEN "111" => y <= '1'; WHEN OTHERS => y <= '0'; END CASE; END PROCESS; END rtl;

6 School of Engineering Variablen Variablen kann man benutzen, um innerhalb eines Prozesses oder eines Unterprogramms einen Wert temporär zu speichern VARIABLE variablen_name : type [:= initialisierung]; VARIABLE summe : std_logic_vector (2 downto 0) := 101 ; Zuweisungsoperator := Beispiel:

7 School of Engineering Kann man nur in Prozessen oder Unterprogrammen benutzen. Werden deshalb zwischen den Zeilen Prozess und Begin definiert. Variablen müssen vor Gebrauch initialisiert werden. Sind Global nicht verfügbar (ausserhalb des Prozess) Will man Variablen ausserhalb eines Prozesses weiterbenutzen, muss man Sie einem Signal zuweisen. Sind nach der Zuweisung sofort gültig, nicht erst beim Verlassen des Prozesses. Können als Index oder temporärer Speicher innerhalb eines Prozesses benutzt werden. Zuweisung durch := Variablen

8 School of Engineering Variablen: weitere Beispiele Extract from Schaltungsdesign mit VHDL, Lehmann, Wunder, Selz, S.153 ENTITY mult IS PORT (a, b : IN integer := 0; y : OUT integer) ; END mult ; ARCHITECTURE number_one OF mult IS BEGIN PROCESS (a,b) -- Aktivierung durch Ereignisse auf a oder b VARIABLE v1, v2 : integer := 0 ; BEGIN v1 := 3 * a + 7 * b ; -- sequent. Variablenzuweisung v2 := a * b + 5 * v1 ; -- sequent. Variablenzuweisung y <= v1 + v2 ; -- sequent. Signalzuweisung END PROCESS ; END number_one ;

9 School of Engineering Variablen: weitere Beispiele Extract from lcddriver.vhd (used in GPS_Uhr project) … type CHAR_RAM_TYPE is array(0 to 79) of std_logic_vector(7 downto 0); signal charRAM: CHAR_RAM_TYPE := (others=>x"00"); … CharRAMWrite : process(clk) variable add : integer range 0 to 79; begin if (clk'event and clk='1') then if (wen='1') then add := to_integer(unsigned(charNum)); charRAM(add) <= dIn; end if; end process; … Achtung: Eine Variable muss vor Gebrauch zugewiesen werden!

10 School of Engineering Variablen exp_var: PROCESS (clk, reset) variable correct_v : std_logic; begin IF reset = '1' then a <= '0'; b <= '0'; ELSIF clkevent AND clk = 1 THEN correct_v := c and d; a <= e or correct_v; b <= f or correct_v; END IF; END PROCESS exp_var;

11 School of Engineering Variable korrekt benutzt

12 School of Engineering exp_var: PROCESS (clk, reset) variable incorrect_v : std_logic; BEGIN IF reset = '1' THEN a <= '0'; b <= '0'; ELSIF clk'event AND clk='1' THEN a <= e or incorrect_v; b <= f or incorrect_v; incorrect_v := c and d; END IF; END PROCESS exp_var; Eine Variable muss vor Gebrauch zugewiesen werden! Falsche Benutzung einer Variablen (1)

13 School of Engineering Variable falsch benutzt

14 School of Engineering Schlechtes Beispiel Extract from lcddriver.vhd (used in GPS_Uhr project) … -- Tick Generation subtype TICK_COUNTER_TYPE is integer range 0 to tickNum; signal tick: std_logic; … TickGen : process(clk) variable tickCounter : TICK_COUNTER_TYPE; begin if (clk'event and clk='1') then if (tickCounter = 0) then tickCounter := TICK_COUNTER_TYPE'high-1; tick <= '1'; else tickCounter := tickCounter - 1; tick <= '0'; end if; end process; Generiert Speicher, da Variable vor Initialisierung gebraucht Für dieses Beispiel nimmt man besser ein Signal

15 School of Engineering Synthese Tick Counter

16 School of Engineering Signale vs. Variablen SignaleVariablen Existieren global in der gesamten Architektur Nur lokal im Prozess lesbar Werden am Ende des Prozesses aktualisiert. Werden immer sofort aktualisiert Werden zwischen Architectur und Begin deklarieret Werden zwischen Process und Begin deklarieret Zuweisung v <= 1Zuweisung v := 1 Achtung: Eine Variable muss vor Gebrauch zugewiesen werden!

17 School of Engineering Architecture Types - rtl (register-transfer-logic: synthesisable) - behav (behavioural: testbench ) - struct (structural: hierarchy)

18 School of Engineering Architecture examples: rtl …extracts of counter.vhd Ueb5-Auf2… architecture rtl of counter is signal next_countL: unsigned(3 downto 0); signal countL: unsigned(3 downto 0); begin comb_increment: process (load,enable,data,countL) begin if (load = '1') then next_countL <= unsigned(data); elsif (enable = '1') then next_countL <= countL + 1; else next_countL <= countL; end if; end process; reg_increment: process (clk,reset) begin if (reset = '1') then countL <= "0000"; elsif(clk'event and clk = '1') then countL <= next_countL; end if; end process; count <= std_logic_vector(countL); end rtl;

19 School of Engineering Architecture examples: behav …extracts of testbench_wuerfel.vhd… ARCHITECTURE behav OF testbench_wuerfel IS COMPONENT wuerfel_ifelse PORT ( Q2, Q1, Q0 : IN std_logic; A, B, C, D : OUT std_logic ); END COMPONENT; … BEGIN … STIMULUS: PROCESS BEGIN tin <= "000" ; WAIT FOR 10 ns; tin <= "001" ; WAIT FOR 10 ns; ASSERT (tout_if = "0001") REPORT "expected tout_if = 0001 " SEVERITY error; WAIT FOR 100 ns; tin <= "010" ; WAIT FOR 10 ns; ASSERT (tout_if = "1000") REPORT "expected tout_if = 1000 " SEVERITY error; WAIT FOR 100 ns; ASSERT false REPORT " --- ALL TESTS PASS ---" SEVERITY failure; WAIT; END PROCESS; END behav;

20 School of Engineering Architecture examples: behav …extracts of testbench_abstimm_case.vhd… ARCHITECTURE behav OF testbench_abstimm_case IS COMPONENT abstimm PORT ( a,b,c : IN std_logic; y : OUT std_logic ); END COMPONENT; … SIGNAL tin : std_logic_vector(2 DOWNTO 0); SIGNAL tout : std_logic_vector(2 DOWNTO 0); BEGIN -- Block Instantiations dut1: abstimm PORT MAP( a => tin(2), b => tin(1), c => tin(0), y => tout(2)); …

21 School of Engineering Architecture examples: behav …extracts of testbench_abstimm_case.vhd… STIM_CHK: PROCESS -- DECLARE PROCEDURE TO AVOID REPEATING TEST STATEMENTS PROCEDURE single_test (tin_test : IN std_logic_vector; tout_test: IN std_logic) IS BEGIN tin <= tin_test; WAIT FOR 10 ns; ASSERT ((tout(2) = tout_test) AND (tout(1) = tout_test) AND (tout(0) = tout_test)) REPORT "test failed for 1 or more duts!" SEVERITY error; WAIT FOR 40 ns; END PROCEDURE single_test; BEGIN single_test("000",'0'); single_test("001",'0'); single_test("010",'0'); single_test("011",'1'); … -- END SIMULATION ASSERT false REPORT " --- ALL TESTS PASS ---" SEVERITY failure; END PROCESS; END behav;

22 School of Engineering Architecture examples: struct …extracts of top_max.vhd… ARCHITECTURE struct OF top_max IS -------------------------- -- COMPONENT DECLARATIONS -------------------------- COMPONENT count_updown GENERIC(n : natural; ov_value : unsigned ); PORT ( clock : in std_logic; reset_n : in std_logic; cntup : in std_logic; count : out std_logic_vector(n-1 downto 0)); END COMPONENT; COMPONENT sieben_seg_ctrl PORT(…) END COMPONENT; -------------------------- -- SIGNAL & CONSTANT DECLARATIONS -------------------------- CONSTANT Low : std_logic := '0'; CONSTANT High : std_logic := '1'; CONSTANT breite : natural :=26; CONSTANT ueberlauf : unsigned := TO_UNSIGNED(49999999,N); SIGNAL m_count : std_logic_vector(N-1 DOWNTO 0);

23 School of Engineering Architecture examples: struct …extracts of top_max.vhd… … BEGIN -------------------------- -- DUT INSTANTIATIONS -------------------------- dut_count: count_updown GENERIC MAP( n => breite, ov_value => ueberlauf) PORT MAP( clock => clock, reset_n => reset_n, cntup => ctrl, count => m_count); dut_sseg : sieben_seg_ctrl PORT MAP(…) END struct;

24 School of Engineering VHDL Fallen

25 School of Engineering 25 Sauber_so: process(s) BEGIN If s = '1' THEN x <= '1' ; ELSE x <= '0'; END IF; END PROCESS; autsch: process(s) BEGIN If s = '1' THEN x <= '1' ; END IF; END PROCESS; elegant: process(s) BEGIN x <= '0'; If s = '1' THEN x <= '1' ; END IF; END PROCESS; 12 3 VHDL Fallen

26 School of Engineering 26 12 3 >1 S X XS XS Process: sauber_so Process: autsch Process: elegant Latch VHDL Fallen