原程序:
z <= a + b + c + d;
打拍:
z1 <= a + b ;
z2 <= c + d ;
z <= z1 + z2;
可是ISE时序分析的结果是打拍后延时更大:
(1)z1 <= a + b + c + d;
Timing constraint:
TS_clk = PERIOD TIMEGRP "clk" 2 ns HIGH 50%;
0 paths analyzed, 0 endpoints analyzed, 0 failing endpoints 0 timing errors detected. (0 component switching limit errors) Minimum period is 1.316ns. (2)z1 <= a + b ;z2 <= c + d ;
z <= z1 + z2;
Timing constraint: TS_clk = PERIOD TIMEGRP "clk" 2 ns HIGH 50%;
55 paths analyzed, 20 endpoints analyzed, 19 failing endpoints 19 timing errors detected. (19 setup errors, 0 hold errors, 0 component switching limit errors) Minimum period is 3.832ns.
是我理解有误么?