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ÔËËãÀàÐÍ ÔËËã²Ù×÷·û NOT, AND, NAND,OR Âß¼ÔËËã NOR, XOR, XNOR ²Ù×÷ÊýÀàÐÍ BIT, BIT_VECTOR, STD_LOGIC, STD_LOGIC_VECTOR STD_ULOGIC, STD_ULOGIC_VECTOR ËãÊõÔËËã·û ±È½ÏÔËËã·û ÒÆÎ»ÔËËã·û ²¢ÖÃÔËËã·û +, ¡ª, *, /, ** =, /=, <, >, <=, >= sll, srl, sla, sra, rol, ror &£¬(, , ,) INTEGER, SIGNED, UNSIGNED ÈÎÒâÊý¾ÝÀàÐÍ BIT_VECTOR STD_LOGIC, STD_LOGIC_VECTOR, STD_ULOGIC STD_ULOGIC_VECTOR, SIGNED, UNSIGNED WHENÓï¾ä WHENÓï¾äÊÇÒ»ÖÖ»ù±¾µÄ²¢·¢ÃèÊöÓï¾ä£¬ÓÐÁ½ÖÖÐÎʽ£ºWHEN/ELSEºÍWITH/SELECT/WHEN¡£ WHEN/ELSEÓï·¨½á¹¹£º assignment WHEN condition ELSE assignment WHEN condition ELSE ¡; WITH/SELECT/WHENÓï·¨½á¹¹ WITH identifier SELECT assignment WHEN value, assignemnt WHEN value, ¡;
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¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª-with WHEN/ELSE¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª- Output <= ¡°000¡± WHEN (inp = ¡®0¡¯ OR reset = ¡®1¡¯) ELSE ¡°001¡± WHEN ctl = ¡®1¡¯ ELSE ¡°010¡±;
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Output <= ¡°000¡± WHEN reset, ¡°111¡± WHEN set,
UNAFFECTED WHEN OTHERS;
¶ÔÓÚWHENÓï¾ä£¬WHEN valueµÄÃèÊö·½Ê½ÓÐÒÔϼ¸ÖÖ£º WHEN value ¨CÕë¶Ôµ¥¸öÖµ½øÐÐÅÐ¶Ï WHEN value1 to value2 ¨CÕë¶Ôȡֵ·¶Î§½øÐÐÅÐ¶Ï WHEN value1 | value2 | ¡ ¨CÕë¶Ô¶à¸öÖµ½øÐÐÅÐ¶Ï GENERATEÓï¾ä
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label: FOR identifier IN range GENERATE (concurrent assignments) END GENERATE
GENERATEÓï¾ä»¹ÓÐÁíÒ»ÖÖÐÎʽ£ºIF/GENERATE£¬´Ë´¦²»ÔÊÐíʹÓÃELSE¡£IF/GENERATE¿ÉÒÔǶÌ×ÔÚFOR/GENERATEÄÚ²¿Ê¹Ó᣷´Ö®ÒàÈ»¡£ Label1: FOR identifier IN range GENERATE ¡¡
Label2: IF condition GENERATE (concurrent assignments) END GENERATE; ¡¡
END GENERATE; Àý£º
SIGNAL x: BIT_VECTOR(7 DOWNTO 0); SIGNAL y: BIT_VECTOR(15 DOWNTO 0);
SIGNAL z: BIT_VECTOR(7 DOWNTO 0); ¡¡
G1: FOR i IN x¡¯RANGE GENERATE z(i) <= x(i) AND y(i+8); END GENERATE;
GENERATEÖÐÑ»·²Ù×÷µÄÉϽçºÍÏÂ½ç±ØÐëÊǾ²Ì¬µÄ£¬ÔÚʹÓùý³ÌÖл¹Òª×¢Òâ¶àÖµÇý¶¯ÎÊÌâ¡£ Àý£º
OK: FOR i IN 0 TO 7 GENERATE
Output(i) <= ¡®1¡¯ WHEN (a(i) AND b(i)) = ¡®1¡¯ ELSE ¡®0¡¯; END GENERATE;
¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª NotOK: FOR i IN 0 TO 7 GENERATE
accum <= ¡°1111_1111¡± WHEN (a(i) AND b(i)) = ¡®1¡¯ ELSE ¡°0000_0000¡±; END GENERATE;
¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª- NotOK: FOR i IN 0 TO 7 GENERATE Accum <= accum + 1 WHEN x(i) = ¡®1¡¯; END GENERATE;
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Simple BLOCK½ö½öÊǶÔÔÓдúÂë½øÐÐÇøÓò·Ö¸î£¬ÔöÇ¿Õû¸ö´úÂëµÄ¿É¶ÁÐԺͿÉά»¤ÐÔ¡£Óï·¨½á¹¹ÈçÏ£º label£ºBLOCK [ declarative part] BEGIN
(concurrent statement) END BLOCK label;
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block1: BLOCK BEGIN
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END BLOCK block1; ¡
block2: BLOCK BEGIN ¡
END BLOCK block2; ¡
END example;
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SIGNAL a: STD_LOGIC; BEGIN
a <= input_sig WHEN ena = ¡®1¡¯ ELSE ¡®z¡¯; END BLOCK b1;
¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª- ÎÞÂÛÊÇsimple BLOCK»¹ÊÇguarded BLOCK£¬ÆäÄÚ²¿¶¼¿ÉÒÔǶÌׯäËûµÄBLOCKÓï¾ä£¬ÏàÓ¦µÄÓï·¨½á¹¹ÈçÏ£º label1: BLOCK
[¶¥²ãBLOCKÉùÃ÷²¿·Ö] BEGIN
[¶¥²ãBLOCK²¢·¢ÃèÊö²¿·Ö] label2: BLOCK
[ǶÌ×BLOCKÉùÃ÷²¿·Ö] BEGIN
[ǶÌ×BLOCK²¢·¢ÃèÊö²¿·Ö] END BLOCK label2;
[¶¥²ãBLOCKÆäËû²¢·¢ÃèÊöÓï¾ä] END BLOCK label1£»
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[VARIABLE name type [range] [ := initial_value; ]] BEGIN
(˳ÐòÖ´ÐеĴúÂë) END PROCESS [label];
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IF (x < y) temp := ¡°1111_1111¡±;