关于ISE布线约束问题请教大神。

tobias

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& \9 A( I4 A, e" W  _) gPlace:866 - Not enough valid sites to place the following IOBs:
& [$ L4 v8 ^+ _. X' B) d   IO Standard: Name = LVCMOS25, VREF = NR, VCCO = 2.50, TERM = NONE, DIR =
   BIDIR, DRIVE_STR = NR
; ^; b& A+ G5 b- M, {$ t6 G1 i           IO_x_x_x_x_x_x_x
/ D9 h, H- u3 i6 A           IO_x_x_x_x_x_x
6 `9 }! I* o% C* C# @5 p+ }8 b  G           IO_x_x_x_x_x
3 a$ [2 x" ]1 e           IO_x_x_x_x
& n' o0 b# x- E9 }8 Y) U           IO_x_x_x
2 }' c- {3 ^5 ^& r           IO_x_x
; ^- Y0 V* S% N4 C: n  X  n' ]           IO_x
$ A" {) y$ c: j$ G) R           IO
3 M5 H9 f+ a, b. c
   This may be due to either an insufficient number of sites available on the
   device, too many prohibited sites,
   or incompatible I/O Standards locked or range constrained to I/O Banks with
   valid sites.
/ f/ n' C4 n( P; i       This situation could possibly be resolved by one (or all) of the
   following actions:
& N0 \2 T5 F8 i0 |   a) Grouping IOBs of similar standards into a minimum amount of I/O Banks by
/ v! t2 ]& d; U" h* s$ w, I8 y   using LOC or range constraints.
   b) Maximizing available I/O Banks resources for special IOBs by choosing
   lower capacity I/O Banks if possible.
8 U8 Y( U& P7 u3 Q4 N) k   c) If applicable, decreasing the number of user prohibited sites or using a
, P  {$ Y6 T3 X$ I   larger device.
. @# i7 C9 C# {' K! h我UCF里根本没有用到LVCMOS25。warnings里也没什么异常啊。
请教大神，非常感谢！
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Demyar

路过帮顶。