将GCLK输入连接到多个PLL

我有一个使用3个PLL的LX45T设计。
简而言之，它们是：
（1）Fvco = 800 MHz，使用bank 3中的MCB为400MHz DDR3 dRAM提供时钟;
它是由MIG产生的，除了输入是GCLK4（存储区1的下半部分）上的（单端）50 MHz时钟，我已经进行了必要的调整，还增加了200 MHz的全局时钟输出。
MIG实例化一个IBUFG，其输出直接连接到PLL（虽然我猜BUFIO2在那里被推断），并且也从包装器输出信号sys_clk_buf。
它还实例化BUFPLL_MCB。
（2）Fvco = 750 MHz，输出125 MHz和250 MHz全局时钟（我已经实例化了BUFG）以及750 MHz I / O时钟，我用它来对上半部分的125 Mb / s输入进行过采样
银行1，我已经实例化了BUFPLL
（3）Fvco = 600 MHz，提供120 MHz全局时钟，我已经实例化了一个BUFG
如果我从sys_clk_buf中获取（2）和（3）中的一个，而从另一个全局时钟中获取另一个，则ISE很满意。
但是，如果我从sys_clk_buf中同时获取（2）和（3）它表示没有BUFPLL_MCB的站点，也没有（2）中的BUFPLL，并且“map”崩溃。
关于PLL连接的限制，ug382还不是很清楚，但我认为GCLK4可以通过BUFIO2_X4Y19连接两个PLL，另外两个通过BUFIO2_X3Y11连接（我没有使用GCLK8）。
也许BUFIO2需要实例化，还是什么？



以下为原文

I've got a design in an LX45T that uses 3 PLLs. Briefly, they are:

(1) Fvco = 800 MHz, sourcing clocks for a 400MHz DDR3 dRAM using the MCB in bank 3; it's as produced by the MIG except that the input is a (single-ended) 50 MHz clock on GCLK4 (bottom half of bank 1) and I've made the necessary adjustments and also added a 200 MHz global clock output. The MIG instantiates an IBUFG, the output of which is connected directly to the PLL (though I guess a BUFIO2 gets inferred there) and is also exported from the wrapper as signal sys_clk_buf. It also instantiates a BUFPLL_MCB.

(2) Fvco = 750 MHz, sourcing 125 MHz and 250 MHz global clocks (for which I've instantiated BUFGs) and also a 750 MHz I/O clock which I use for oversampling some 125 Mb/s inputs in the top half of bank 1, and for which I've instantiated a BUFPLL

(3) Fvco = 600 MHz, sourcing a 120 MHz global clock for which I've instantiated a BUFG

ISE is happy with that if I source one of (2) and (3) from sys_clk_buf and the other from one of the global clocks. But if I source both (2) and (3) from sys_clk_buf it says there are no sites for the BUFPLL_MCB, nor for the BUFPLL in (2), and "map" crashes.

ug382 isn't very clear about what the restrictions are for connections to PLLs, but I would have thought GCLK4 could connect to two PLLs through BUFIO2_X4Y19 and two more through BUFIO2_X3Y11 (I'm not using GCLK8). Maybe the BUFIO2s need to be instantiated, or something?