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1、Library IEEE ; use IEEE.std_logic_1164.all ; use IEEE.std_logic_arith.all ;ENTITY counters ISPORT ( d: IN INTEGER RANGE 0 TO 255; clk: IN BIT; clear: IN BIT; ld: IN BIT; enable: IN BIT; up_down : IN BIT; qa: OUT INTEGER RANGE 0 TO 255; qb: OUT INTEGER RANGE 0 TO 255; qc: OUT INTEGER RANGE 0 TO 255;
2、qd: OUT INTEGER RANGE 0 TO 255; qe: OUT INTEGER RANGE 0 TO 255; qf: OUT INTEGER RANGE 0 TO 255; qg: OUT INTEGER RANGE 0 TO 255; qh: OUT INTEGER RANGE 0 TO 255; qi: OUT INTEGER RANGE 0 TO 255; qj: OUT INTEGER RANGE 0 TO 255; qk: OUT INTEGER RANGE 0 TO 255; ql: OUT INTEGER RANGE 0 TO 255; qm: OUT INTE
3、GER RANGE 0 TO 255; qn: OUT INTEGER RANGE 0 TO 255 );END counters;ARCHITECTURE a OF counters IS BEGIN - An enable counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; BEGIN IF (clkEVENT AND clk = 1) THEN IF enable = 1 THEN cnt := cnt + 1; END IF; END IF;qa= cnt;END PROCESS;- A synchronous load
4、 counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; BEGIN IF (clkEVENT AND clk = 1) THEN IF ld = 0 THEN cnt := d; ELSE cnt := cnt + 1; END IF; END IF;qb=cnt; END PROCESS;- A synchronous clear counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; BEGIN IF (clkEVENT AND clk = 1) THEN IF c
5、lear = 0 THEN cnt := 0; ELSE cnt := cnt + 1; END IF; END IF;qc=cnt;END PROCESS;- An up/down counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; VARIABLEdirection : INTEGER; BEGIN IF (up_down = 1) THEN direction := 1; ELSEdirection := -1; END IF;IF (clkEVENT AND clk = 1) THEN cnt := cnt + dire
6、ction; END IF;qd=cnt;END PROCESS;- A synchronous load enable counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; BEGIN IF (clkEVENT AND clk = 1) THEN IF ld = 0 THEN cnt := d; ELSE IF enable = 1 THEN cnt := cnt + 1; END IF; END IF; END IF;qe=cnt;END PROCESS;- An enable up/down counter PROCESS
7、(clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; VARIABLEdirection : INTEGER; BEGIN IF (up_down = 1) THEN direction := 1; ELSE direction := -1; END IF;IF (clkEVENT AND clk = 1) THEN IF enable = 1 THEN cnt := cnt + direction; END IF;END IF;qf=cnt;END PROCESS;- A synchronous clear enable counter PROCESS (cl
8、k) VARIABLEcnt: INTEGER RANGE 0 TO 255; BEGIN IF (clkEVENT AND clk = 1) THEN IF clear = 0 THEN cnt := 0; ELSE IF enable = 1 THEN cnt := cnt + 1; END IF; END IF; END IF;qg=cnt;END PROCESS;- A synchronous load clear counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; BEGIN IF (clkEVENT AND clk
9、= 1) THEN IF clear = 0 THEN cnt := 0; ELSE IF ld = 0 THEN cnt := d; ELSE cnt := cnt + 1; END IF; END IF; END IF;qh=cnt;END PROCESS;- A synchronous load up/down counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; VARIABLEdirection : INTEGER; BEGIN IF (up_down = 1) THEN direction := 1; ELSE dir
10、ection := -1; END IF;IF (clkEVENT AND clk = 1) THEN IF ld = 0 THEN cnt := d; ELSE cnt := cnt + direction; END IF; END IF;qi=cnt;END PROCESS;- A synchronous load enable up/down counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; VARIABLEdirection : INTEGER; BEGIN IF (up_down = 1) THEN directio
11、n := 1; ELSE direction := -1; END IF;IF (clkEVENT AND clk = 1) THEN IF ld = 0 THEN cnt := d; ELSE IF enable = 1 THEN cnt := cnt + direction; END IF; END IF; END IF;qj=cnt;END PROCESS;- A synchronous clear load enable counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; BEGIN IF (clkEVENT AND c
12、lk = 1) THEN IF clear = 0 THEN cnt := 0; ELSE IF ld = 0 THEN cnt := d; ELSE IF enable = 1 THEN cnt := cnt + 1; END IF; END IF; END IF; END IF;qk=cnt;END PROCESS;- A synchronous clear up/down counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; VARIABLEdirection : INTEGER; BEGIN IF (up_down = 1
13、) THEN direction := 1; ELSE direction := -1; END IF;IF (clkEVENT AND clk = 1) THEN IF clear = 0 THEN cnt := 0; ELSE cnt := cnt + direction; END IF; END IF;ql=cnt;END PROCESS;- A synchronous clear enable up/down counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; VARIABLEdirection : INTEGER; B
14、EGIN IF (up_down = 1) THEN direction := 1; ELSE direction := -1; END IF;IF (clkEVENT AND clk = 1) THEN IF clear = 0 THEN cnt := 0; ELSE IF enable = 1 THEN cnt := cnt + direction; END IF; END IF; END IF;qm =cnt;END PROCESS;- A modulus 200 up counter PROCESS (clk) VARIABLEcnt: INTEGER RANGE 0 TO 255; CONSTANT modulus : INTEGER := 200; BEGIN IF (clkEVENT AND clk = 1) THEN IF cnt = modulus THEN cnt := 0; ELSE cnt := cnt + 1; END IF; END IF;qn=cnt;END PROCESS; END a;
