原工程是在xilinx sp-6芯片上的现在想在v-6的评估板上跑，所以我用PlanAhead来改了管脚约束，然后保存了。但是打开ucf一看发现管脚约束一点都没变，然后布线的时候也发生报错。求大神来指导怎么能成功用PlanAhead直接改ucf文件。。下面是ucf文件###########################################################时钟和复位接口
NET "ext_clk_25m" LOC = P23;
NET "ext_clk_25m" IOSTANDARD = LVCMOS33;
NET "ext_rst_n" LOC = H17;
NET "ext_rst_n" IOSTANDARD = LVCMOS33;

##########################################################
#LED指示灯接口
NET "led[0]"                LOC=P17   | IOSTANDARD = LVCMOS33;
NET "led[1]"                LOC=P16   | IOSTANDARD = LVCMOS33;
NET "led[2]"                LOC=P15   | IOSTANDARD = LVCMOS33;
NET "led[3]"                LOC=P14   | IOSTANDARD = LVCMOS33;
NET "led[4]"                LOC=P12   | IOSTANDARD = LVCMOS33;
NET "led[5]"                LOC=P11   | IOSTANDARD = LVCMOS33;
NET "led[6]"                LOC=P10   | IOSTANDARD = LVCMOS33;
NET "led[7]"                LOC=P9    | IOSTANDARD = LVCMOS33;

##########################################################
#拨码开关接口
NET "switch[0]"                LOC=P29   | IOSTANDARD = LVCMOS33;
NET "switch[0]" LOC = L20;
NET "switch[1]"                LOC=P30   | IOSTANDARD = LVCMOS33;
NET "switch[1]" LOC = L21;
NET "switch[2]"                LOC=P32   | IOSTANDARD = LVCMOS33;
NET "switch[2]" LOC = C22;
NET "switch[3]"                LOC=P33   | IOSTANDARD = LVCMOS33;


NET "led[0]" LOC = AC22;
NET "led[1]" LOC = AC24;
NET "led[2]" LOC = AE22;
NET "led[3]" LOC = AE23;
NET "led[4]" LOC = AB23;
NET "led[5]" LOC = AG23;
NET "led[6]" LOC = AE24;
NET "led[7]" LOC = AD24;


NET "led[7]" IOSTANDARD = LVCMOS25;


NET "ext_clk_100m" LOC = U23;
NET "switch[3]" LOC = D22;


NET "led[6]" IOSTANDARD = LVCMOS25;
NET "led[5]" IOSTANDARD = LVCMOS25;
NET "led[4]" IOSTANDARD = LVCMOS25;
NET "led[3]" IOSTANDARD = LVCMOS25;
NET "led[2]" IOSTANDARD = LVCMOS25;
NET "led[1]" IOSTANDARD = LVCMOS25;
NET "led[0]" IOSTANDARD = LVCMOS25;
NET "switch[3]" IOSTANDARD = LVCMOS25;
NET "switch[2]" IOSTANDARD = LVCMOS25;
NET "switch[1]" IOSTANDARD = LVCMOS25;
NET "switch[0]" IOSTANDARD = LVCMOS25;

# PlanAhead Generated IO constraints

NET "ext_clk_100m" IOSTANDARD = LVCMOS25;
NET "ext_rst_n" IOSTANDARD = LVCMOS25;



我改了planahead发现下面多了几行是不是我直接吧以前的删掉就能用了
求解答